Negative fuel trims when accelerating

HTTP/1.1 200 OK Date: Fri, 23 Jul 2021 08:23:55 GMT Server: Apache/2.4.6 (CentOS) PHP/5.4.16 X-Powered-By: PHP/5.4.16 Connection: close Transfer-Encoding: chunked Content-Type: text/html; charset=UTF-8 207e 14 Jan 2016 . In order to do a diagnostic on the MAF, you need to use a scan tool, select the PID data menu and while the engine is running, read the fuel trim values. The VVE is tuned, I just choose not to use it. I thought that a negative fuel trim meant that the PCM was dialing back the fuel due to to much fuel (rich which is what I beleive - tail pipe is kinda sooty, not as bad as when I started) and the fuel mileage even on the highway running slower and long distance is never better than 20 (my 99 got consistently 25, even cleared 30 on 1 tank of . Similarly, if the fuel trims are reading negative, the fuel . 5%. For a minute or so rev and hold the engine at 1500 to 2000 RPM, take a look on STFT, if the values is drop back to the more normal reading, it tell you at idle there a vacuum leaks on the engine. The ONLY way to tell if the Trims you have are causing a Problem, is to Add a Wideband O2 Sensor and see. The short term goes to as low as -20% especially at deceleration. During "closed-loop" operation, the PCM reports changes in fuel trim calculations via the OBD II generic data parameters short-term and long-term fuel trim. Note: This DTC is very similar to P0171 Pontiac, and in fact your vehicle may show both codes at . 02 Mar 2018 . if you have access to a wideband try that. That said, a leaky spider would result in negative fuel trims, not positive. It would crank up run a few seconds and die like very low of . I am thinking that fuel delivery is not consistent across the banks probably because at least 1 injector is leaking/faulty or O-rings. My fuel trims are way out there on the negative side. 7 mil status off abslt tps % 26. 85 to 0. Fuel Trims are adjustments that a Engine Control Unit (ECU) applies to compensate in changes in environmental variables to ensure the motor remains on its factory base map (usually stoich) in the 'Closed Loop' mode. The ECU controls Air/Fuel mixture in order to maintain power, efficiency, and emissions. While on idle, OBD2 continuously read STFT (short term fuel trim) high at 10 to 30%, again with similar numbers for both banks. I have been receiving intermittent high negative long term fuel trims (-10 to -12%) at idle. Long Fuel Trim reading -29. Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and base engine issues such as low compression and incorrect camshaft timing. 6 fluctuates. A normal long-term fuel trim reading will appear to stay the same, giving a . Short Term Fuel Trim Description The short term fuel trim is a PCM erasable memory register. Negative fuel trim is caused by 'richer' combustion than the ECM of PCM predicted. We also talked a bit about the factors that can cause fuel control to get. And anything above 10 + or - when you add the long term and short term numbers is a sign of a problem. 11 Mar 2015 . IGNITION TIMING. This does get better around -8% under load, but the long term trim never reaches positive values or even 0. if you have access to a wideband try that. A scan tool can read the fuel trim. Bank 2 will always be slightly higher as the supercharger rests above that bank and additional fuel along with pulled timing are strategies the PCM utilizes to keep that . Short-term fuel trim - a percentage of fuel change that effects the current cel of the map you are in. 7% both in positive and negative forms and indicates a proper running condition both on the lean and rich scale. To better understand how fuel trim numbers are generated, the ECM/PCM uses the oxygen sensor or air/fuel sensor input signal to adjust fuel injector pulse . Once released after a little while they start to go back. 21 Jan 2013 . NEGATIVE (-) fuel trim values mean the engine computer is subtracting fuel (decreasing the pulse width or on-time of the fuel injectors) to reduce the amount of fuel injected into the engine. Although based on ideaology the goal is to keep LTFT as close to zero as possible to maintain that ideal 14. Id expect 0 to 5% positive or negative fuel trims on a good car. Your vehicle is getting too much air and not enough fuel, creating a lean condition that disrupts the fuel efficiency of your vehicle. 2 Grams/sec Mass air flow at 770 RPM. Everything seems to be running. ) Here is an explanation of fuel trim and what it does for us. I believe there are positive and negative fuel trims, . A normal long-term fuel trim reading will appear to stay the same, giving a . Conversely, a negative fuel trim indicates that the ECU is reducing the fuel delivery for that range, meaning that the MAF scaling in that range is slightly too high. The guy told me that if I had a code reader that could be programmed to read Long Term Fuel Trim then I would likely see the values somewhere in the negative double digits, typically around -15. My fuel trims remain high at idle (ltft 25%, stft from - 3% to around +10%), and lower when under load, especially if I'm actually driving. If the engine is running properly, fuel trims should be close to zero. It depends on the response of the O2 sensor. Engine is running lean if values of the STFT (Short Term Fuel Trim) and LTFT (Long Term Fuel Trim) higher than +10. and your Os sensor voltages tank to lean (0 volts on conventional O2, and hits over 3. In the React phase, the PCM commands the fuel injector to stay open longer. You can see as I start to accelerate from a stop the RPM increases to 1300ish for a split second and then falls to 600ish before jumping rapidly . At freeway speeds fuel trim is close +/-5% on both banks, short and long term. I used my scan software to check things out and the Long Term Fuel Trim (Bank 1) is at 19. However the ECU was showing both rich or lean fuel trims at different times. You will know what causes the computer to do the compensation by checking the “numbers” of the Fuel Trim from the full range of operating conditions. Here's what I think was happening: The MAF was starting to fail and to under-measure the air flowing through it . On newer vehicles, the fuel trims should be no more than 5%. Series I as well, but will need different scan tool) Most common causes- loose or cracked gas cap, bad fuel pressure regulator, bad MAF sensor, clogged air filter or collapsed air intake duct . Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and base . I'm having some trouble with negative long term fuel trim . I removed the Intake cover and found puddles of Oil in there, which led me to replace the PCV. The bottom two are the Long term fuel trims 1 and 2. Now most will say pull negative battery cable and pull head light switch right, I will tell you in my case that did not work. I have a 1999 Tacoma Prerunner 3. The long-term fuel trim can vary depending on the altitude. So that would indicate a richer than normal air fuel mixture somewhere in the intake system. 08/1. Fuel trim reading about negative 25 now. However, it’s not enough to check fuel trims while idling. #11 · 2 mo ago. #5 • Jul 6, 2011 (Edited) camillianeyez02 said: I have a Pontiac G6 2008 4cyl and I just recently started having an issue with the car not accelerating like it use to. Negative numbers represent the PCM removing fuel from the system. A positive voltage on the O2 sensor means it is sensing fuel in the exhaust, negative voltage that it is sensing oxygen in the exhaust. Long term trim will be a slow change. result of heavy acceleration or extended idle conditions . This causes the fuel trim numbers to become negative during a boost situation. Note the fuel trims at idle and increase engine speed to 2500 RPM and hold. A bad O2 sensor won’t necessarily have any negative engine effects with the exception of worse fuel economy. 2031 7 air fuel ratio. 5 LYX. Diagnosing a failed or clogged fuel injector can be tricky but . Why? Maximum power is made between 0. This maf sensor is not within the limits. 6 volts on bank 2 upstream at 65mph. 13 Nov 2017 . 7:1 is critical to emission control Using a scan tool you can monitor “Fuel Trim” to see if engine is running rich or lean. …). MacFadyen on topic Fuel Trims Analyzing. I am assuming this has to do with the reason the engine idles rough and worse when there is a load put on it. If the compression is low, excess raw hydrocarbon will be in the exhaust stream. The long term fuel trims (LTFT) are driven by the short term fuel trims. log o2 voltages and ps_w. This presents three possibilities: Not enough air is reaching the combustion chambers. Please help. My fuel trims are even, LTFTs hover between -1 and +1, so it's not like I have a vacuum leak causing a hesitation. Its. - non linear acceleration/deceleration at low speed. Did Forscan list a Rear O2 Fuel Trim in the PCM data list? Probably not, given the model year, but it might be fun to check. Diagnosis will require testing fuel pressure and the fuel pressure regulator to see if they are operating within specifications. Sluggish performance, acceleration, etc. STFT's act normal, runs fine, but the LTFT pegs out negative. my fuel trim. e. #2 · Oct 12, 2017. 95 Lambda (12. Negative LTFT numbers mean the PCM is delivering less fuel to compensate for a rich fuel condition. Hold Steady Speed. Last. Injector (Number 1,3,5) failed C. Because this is a forced-induction beast, it would be readily explained by a post-turbo, post-MAF leak. Mazda 6, hesitating at lower RPM and negative fuel trim. Fuel filter has about 14,000 miles on it. March 13th, 2018. Hello all, I just analyzed my LTFT's with a OBD II scanner and Bank 2 at idle is reading 6% and increases to 12% at approx 3000 RPM, while Bank 1 reads 3% at idle and increases to 7% at approx. Mariowinax1 · Registered. If the engine is difficult to start when recently run and the LTFTs are showing consistent negative trims at idle then suspect that the fuel pressure regulator is overpressurising the fuel rail. Hello I own a 2005 Infiniti G35. Posts: 11644. My engine will occasionally lope at startup. Short term fuel trim will see the high voltage from the O2 sensor and command a lean correction. under-estimates air flow at high air flows (causes fuel system to go lean). The vapor pressure gets as low as -1700pa under acceleration. Ron addresses the common issues that can cause fuel trims to go negative. ·. The check engine light flashes on/off, (i. In this, the third part of our series on Fuel Trim, we will discuss the feedback components that report what is happening at the end of the line. Fuel trim began due to stricter tailpipe emissions and fuel economy. 250 miles ago, the short block assembly was replaced with an rebuilt unit from Subaru. 5RS with 150k miles. Offline. Negative fuel trim percentages indicate the PCM is Pay very close attention to the Long Term Fuel Trim values because they indicate how much the Powertrain Computer is compensating for an imbalanced air/fuel ratio. The long-term fuel trims (LTFT) are driven by the short-term fuel trims. Codes retrieved were P2178 fuel trim rich at cruise or acceleration bank 1 P2180 fuel trim rich at cruise or acceleration bank 2 P0089 fuel pressure regulator performance P0300 P0301 P0302 P0303 P0304 P0305 P0306 P2189 fuel trim lean at idle bank 2 Vehicle was very hard to start. When the fans turn off, the trims goes back down. From the carburetor, the fuel enters the combustion process as it mixes with air to create the optimal fuel-to-air ratio that your BMW requires to run smoothly. Brand new re-manufactured engine. If the Long Term Fuel Trim is over 10 percent on one bank of cylinders and not the other, there might be a vacuum leak or defective/cracked intake manifold on that specific bank. The computer is either adding or taking away fuel based on what the Air Fuel Ratio (AFR) sensor reads. When checking for fuel mixture issues and fuel trim faults, always perform the same test drive. Problem moved with. I have Ford fusion energi 2013 , and iam facing a bad fuel economy and a bad acceleration , I have conected my bluedriver to the obd port , and this what I have found , I hope some one can help me with these values Long term fuel trim is 7. This 2005 Buick LaCrosse came in with a list of complaints: check engine light, hesitation, stalling out. 12 Mar 2019 . May 7, 2015 ·. When at around 25% throttle and . More details about what is . if you have access to a wideband try that. 5 volts or less, it's reading rich which might explain the negative fuel trim numbers. 622, 112 LSA using HP Tuners. Negative fuel trim numbers caused by minor intake vacuum leaks generally disappear under heavy engine loads. Long-term fuel trims were -8. STFT Every time the STFT maxes out either positive or negative. Why Car Running Rich, Negative Long Term Fuel Trim. REAR FUEL TRIM: Since rear fuel trim (RFT) operating strategies vary widely among manufacturers, you’ll have to learn as you go. 1; 2; Next. no cel or pending code on ecu. If the fuel trims stay within 5% or 10%, then fuel isn’t . Discussion Starter · #9 · Apr 5, 2013. Fuel pressure is in the 38-45 range and climbs when at WOT and high RPM. Upon a RPM increase to 3500RPM my LTFT is -3. took it back to the garage and they hooked up the Snap On advantage scan tool, did a bunch of tests, said the fuel pump . It’s the opposite when accelerating and decelerating in short periods, the short-term fuel trim will go up and down more noticeably. However, the relative newness of this M5 makes me wonder if this is even remotely possible. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed. Discussion Starter · #1 · Dec 11, 2017. Due to high negative fuel trims, a leaking fuel injector will reduce average fuel injector pulse widths from about 2-3 ms to 1. Now we talk about the myth: "learn-around" is caused by constantly changing long-term fuel trims. My STFT on idle running in closed loop is 0. Tags: maf, negative fuel trim, vacuum . Negative fuel trim numbers means that the fuel mixture is richer than . log o2 voltages and ps_w. Finding vacuum leaks and correcting them WILL cause the fuel trims to go more negative. The OBD did detect the Lack of Switch for the HO2S - while the mixture remained stubbornly rich the PCM could not lean it off enough to enable the . M. If your engine is a 4 cylinder, then it has only one bank, Bank 1. Symptoms: Under moderate to heavy throttle it sputters, pops. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage . It then underestimates airflow at cruising speeds, which accounts for the positive fuel trim values. 0. The short term fuel trim (STFT) appears to be consistently taking away fuel as the engine runs. I plotted long term fuel trim, at idle LTFT is down . The long term fuel trims (LTFT) are driven by the short term fuel trims. But the top is Short term fuel trim 1 and the third is STFT2. When the engine gets warm, its idle speed drops to ~620 RPM and sometimes the first oxygen sensor starts reporting that the air-fuel mix is running too rich and the fuel trim starts going down really fast until it reaches -30% and stops there. Which of the following will also be true? A. Yes. I don't know much about fuel trims but from quick reading you want the numbers to be close to 0 as possible. At approximately 13. Here are some possible causes of negative fuel trims, . It will float back to normal, +/- 0-5% but just as quickly peg negative down to the -30's%. 11 May 2016 . You will notice on new vehicles, the fuel trims are +-1% and as a vehicle increases mileage, fuel trims increase (aka deviation is greater). 5 mins at . G8 with cam, no cats, LS7 MAF. Negative fuel trim is caused by ‘richer’ combustion than the ECM of PCM predicted. A positive trim value means the ECM is ADDING fuel at 12-14% above the programmed rate. 2075 What might be. 16 May 2011 . I just bought a OBDII scanner with live data which can see the fuel trims. Currently averaging around -12% long term fuel trim at idle when warm. So if we watch what happens over a period of time, we'll start with possibly quite a large negative short term fuel trim, and then over time the long term fuel trim will take over from that, getting our short terms back to zero. 59/-6. Re: c5 rs6 high negative (partial) fuel trims. I run MAF only. Posts: 11644. The injector pulse width was lengthened. Being able to interpret your scanner Fuel Trim Data requires a basic knowledge of the interaction of Short Term Fuel Trim and Long Term Fuel Trim data. Gas mileage went from 17. Did any of your previous captures show the hesitation in 3rd/4th or when accelerating hard up a hill? If not, could you get a capture of that and post it? Because your trims are pretty good, IMO. You MIGHT see a high positive and negative number for a brief moment, but as long as it isn't like that all the time then I would say everything is acceptable. When the ECU reported the lowest MAF idle grams/second readings, fuel trim went very high. Technician B says when the O2 sensor has a rich signal, the STFT goes lean to adjust the air/fuel ratio. This was second clue about possible fuel delivery problem. I would definitely try resetting the fuel trims and see what that does for you before going much further. Excessive negative fuel trims. 8% - this does not change when accelerating pretty much stays the same. On my '06 2. 15 Mar 2019 . I'm driving a '05 Mazda 6 1. 5 while bank 2 goes to 0 or even negative. A scan tool can read the fuel trim. But for now I’m thinking the recent fuel trim changes are a result of the 91 octane w/o ethanol and partially because of the high humidity in my area leaving less O2 in the mix for the air fuel ratio. Short fuel trim is the immediate response of the ECM/PCM to rich and lean conditions reported by the O2 sensor (primarily the upstream sensor). Negative fuel trim value, contrary to positive one indicates there is either too much fuel or too little air goes to only one bank of cylinders. When observing fuel trim in the scanner data stream, it appears in negative and positive parameters. Since the fuel trims . Fixed vac leak, replaced IAC valve, reset ECU. The fuel burns and powers the car. and the cause could be leak, . The errant Fuel Trims would have generated a DTC eventually, but these need a LTFT lower than perhaps -25% and a STFT lower than perhaps -5% before it would have recorded a negative Fuel Trim DTC. I'm not sure if this will be helpful, but my car has a negative LT fuel trim of -5 to -7% if I recall correctly, and my compression was 150 in all cylinders. Help Negative Fuel Trim. Powertrain and engine control computers (PCM/ECM) employ a long term fuel trim delivery strategy that learns to self-adjust as driving conditions change and the engine wears. values are: STFT B1 : -25% - when accelerating these values come down to -3%/-4% STFT B2 : -23% - when accelerating these values come down to -3%/-4% LTFT B1 : 0. Click to see full answer. MacFadyen on topic Fuel Trims Analyzing. my BAFX scanner said my FT were as follows. These MAF g/s variations were affecting the fuel trim numbers too. It hangs around 10% under revving and 4-7% under load; this has not changed since before the repairs that have been done. I believe there are positive and negative fuel trims, . . And O2's would naturally drift toward higher voltage (NO OXYGEN). Short Term Fuel Trim (STFT) Multiplicative This is the control of the Injection Pulse Time Open over the mid to upper range of engine operation. I usually put in 91 octane fuel from Costco (Top Tier) I do have a GAP Tool and have checked my fuel trims. stft good under acceleration, but goes extreme negatives when coasting then switches to OL drive. The OBDII trouble code P0171 - System Too Lean (Bank 1) means that the engine air-fuel mixture is too lean, or there is too much air and too little fuel. So essentially we should be seeing our short term fuel trims if everything's working well, cycling pretty close to zero. 24 Jul 2015 . The long-term fuel trims (LTFT) are driven by the short-term fuel trims. LTFT refers to changes in STFT but averaged over a longer period of time. Zero PSI at the fuel rail in the mornings before I start the car. This adjustment is called fuel trim and can be read using a scan tool. The engine is not idling very low but there still may be a clue here. From the FSM: p0170=fuel trim malfunction bank 1 (cali spec) common causes: A. 41 in each bank and . i have a v6 2008 6 speed. My LTFT on idle running in closed loop is -22. Negative fuel trim means the fuel mixture is too rich and the car’s computer is cutting back on the amount of fuel it’s delivering to the engine to compensate. pressure test. 1) Possible causes. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). I'm thinking it's probably normal. Car is a 2000 2. Always evaluate fuel trims (STFT) at idle and at 2500 RPM. The fuel trim behavior chart for an air metering issue looks very similar to a fuel volume issue (figure 3), but there are differences. 1 of 2 Go to page. 3000 RPM. on December 10, 2017. 25 (bank 1/bank 2) at cold start. The negative fuel trim value indicates the PCM has been progressively reducing the amount of fuel injected as a result of information returned from the O2 sensor (O2 sensors report a rich condition, the PCM reduces injector duration until the O2 sensor reports a lean condition). Make sure you have spark and the plugs are good. My S10 blazer lacks power, bogs under acceleration, recently truck would not start, took it to a garage and they replaced the injections module (“spider injection module, complete unit", fuel pressure regulator included), truck still lacks power and bogs under acceleration. i have 98 ranger xlt 3. The old OBDII stuff was pretty lienient on how far the Fuel Trims are allowed to go. 65 seconds, the short-term fuel trim (STFT, green trace) begins to go negative and quickly goes to −30%, which indicates that the charcoal canister is rich. I have been getting very poor fuel mileage around town lately (ie 10-12 mpg), and I drive with a light foot. You will know what causes the PCM to do this compensation by checking the Fuel Trim “numbers” within the full range of operating conditions. (See Fig. recently changed two primary o2 sensor and maf sensor with original ones. Much fuel LTFT Bank1 and Bank2 are negative -5% or -6% while driving and my leg on throttle. I understand that if STFT is in negative then this is rich condition and it can impact fuel consumption widely. A majority of the time, the fuel pump is located inside the fuel tank. LTFT B2 : 0. 4 mpg. S1B2 (after cat?) refreshes slowly but predictably, accelerating the numbers go up, . Vehicle was at temperature. For gasoline, that’s about 14. That’s why it’s called short-term fuel trim. . 3) checked fuel trims. Once you’re at a steady speed, the trim will usually be around plus or minus 1% to 2%, at 36,000 miles. The 1594/1594 values effectively disable the high fuel trim selection on a 2G! If you want to re-enable, try these values instead (taken from an EVO3 ECU, which uses the same MAF sensor as a 2G DSM but has high fuel trims enabled!). Posts: 11644. If the measured fuel pressure is higher than spec, I would expect negative fuel trims, not positive. If the STFT immediately decreases and moves to acceptable levels and the LTFT slowly starts to come back down, you have a vacuum leak. Need some help. Positive fuel trims near or above 10% will likely cause “false” catalyst codes. 6 shows fuel trim and volumetric efficiency charts related to the MAF sensor. According to my AP, my LTFT is a little high. log o2 voltages and ps_w. 5 to 14. Short-term fuel trim (STFT) and long-term fuel trim (LTFT) are expressed as a percentage, and the ideal range should be within 5%. 15 Jul 2019 . Which basically means the car is running rich. 34% Bank 2) Short term trims change all the time but when I checked last they were both positive (. 2067 The O2 bank 1 sensor 2 is usually 0. That being said, ideal fuel trims at all time should be below 4. I changed my maf sensor, but it did nothing. 92. 100 volts off so changing out rears and will update my findings. 670 st ftrm11 % -18. Have a 97 Ranger, 2. Accelerate. If it is faulty, a dead spot and hesitation can occur. A bad or dirty MAF can also cause fuel trims to do weird things. The ECM made the Short Term trim change because the extra air was measured by the oxygen sensors. if you have access to a wideband try that. There are two types of fuel trim – short term (STFT) and long term (LTFT). Fuel Trim Diagnosis And O2 Sensor Performance. 1-0. A/F sensors ok. Scanning it and reading about -8% LT when idling. Accelerating at wide-open throttle, fuel trims dropped to zero as the engine showed 94% load. The vapor pressure goes negative when the commanded evaporator purge value increases. His problem of negative fuel trim and going lean during WOT was there when he had the turbo on and continues now that he has the headers. VW Scirocco R 2. Issues like leaking fuel injectors, a defective fuel pressure regulator and defective MAF sensors will be addressed. 1998 Chevy Venture LS Note: Many vehicles will not use fuel trim from the post-cat sensors, in this case fuel trim will be displayed as 99. Go. Alcohol density/fuel trim issues. The short term Fuel trim1 was at -21. 4. 12,441 Posts. Evap system OK. 8% - this does not change when accelerating pretty much stays the same. Engine Interpretation. I have a acceleration problem, idle is good, replaced the fuel pump and fuel filter about 2 months ago, when I press accelerator it vibrates and falls on its face, has 217,000 miles, don’t know th. Also should mention, under acceleration, while moving, engine sounds like a lawn mower. The car has no any code or drivability issues. As the engine operating conditions change, the PCM will switch from cell to cell in order to determine what long-term FT factor to use in the base pulse width equation. Negative fuel trims indicate a rich air/fuel ratio. Accelerating mildly (90% load) around 2500 RPM would naturally send fuel trims positive - even toward dropping out of closed loop. 5# fuel injectors? 245 Posts. C. Incorrect fuel pressure Live data shows neg fuel trims at all times. 9 veh speed mph 6 fuel sys 1 clsd fuel sys 2 n/a o2s11 v 0. ·. Does the STFT oscillate around 0. NEGATIVE (-) fuel trim values mean the engine computer is subtracting fuel (decreasing the pulse width or on-time of the fuel injectors) to reduce the amount of . IDLE TUNING The following is a collection of idle tuning notes, tips ‘n tricks and How-2’s for idle tuning a big cam (or any cam for that matter) that I used when dialing in my 248/254, . Fuel trim is just that. Long term is +24 to +28, and short term is everywhere. Negative trim shows too rich. Did any of your previous captures show the hesitation in 3rd/4th or when accelerating hard up a hill? If not, could you get a capture of that and post it? Because your trims are pretty good, IMO. Oh, you see those fuel trims during deceleration. They are actually negative for long term when I checked last (-. Already changed pump/filter checked fuses etc - all OK. Cat is bad/gamble on a junkyard cat. P0171 is lean and the fuel trims have to add fuel to try and correct for the lean condition. LTFT now ranges between 11% and 20% at idle. 10 May 2017 . Car is a FG XR6T which until the weekend was tuned by a workshop under the previous owner, standard injectors, X-force cat and dump, K&N air filter and no other drivetrain mods. So take the vehicle for a test drive and watch fuel trims when accelerating, cruising, highway speeds and declaration. I also noticed that fuel trim values at idle had too much difference with about -7% total trim on bank 1. The data in the cells can be coloured based on user definable settings to indicate data, in and out of the ideal range. Driving steps here. In positive corrections, fuel is added to adjust for a lean condition, while negative corrections respond to a rich condition. The voltage signal from the oxygen sensor decreased. When a mechanic "Sets your timing" during a tuneup he is adjusting your ignition . 7:1 for a gasoline engine, the fuel trims are based off this ideal air-fuel mixture. The fuel trim calculation is percentage of fuel the computer is adding or removing from the learned base value or adaptation in order to maintain the proper AF ratio. computer always opens injectors longer than 0 STFT, to get instant acceleration Since its rich -18 at idle but resolves quickly with any acceleration AND has no issues at full throttle, im thinking diaphragm or spring defect . I tested for boost leaks and found a fairly big leak so I fixed it. is no longer trying to kick on every time I accelerate, but I'm still getting the "too rich" CEL. BTW running rich will not damage the convertor any where near as fast as what running lean can. Theories/Solution. So I have gotten the fuel trims a lot closer to zero after spending a ton of time with the vve and maf table, but still end up with bank one adding fuel and bank two subtracting fuel right before wot/open loop acceleration. A useful diagnostic tool is to determine if the fuel trim problem exists in more than one engine operating range. However I looked at my fuel trims and bank 1 and 02 sensor seem normal it fluctuates between -. Some things can cause the short term fuel trims to swing more. Edited June 20, 2013 by dballs Long term fuel trim What is long term fuel trim? This article deals with long term fuel trim. 1 st ftrm1 % -21. However, my scan tool tells me that the LTFT is … Thanks. . 59. I scanned my Civic with a scan tool and there were no active or stored codes, but I did notice my fuel trims are close to -10%. Re: c5 rs6 high negative (partial) fuel trims. only when throttle is opened. However, some run high, like five percent. SFT at idle was between -6 and 0 and between -3 and 0 while cruising and WOT. Sir can you tell me step by step process to diagnose negative fuel trim @Xulfiqar?? tuneupgo. The next step is to locate the faulty fuel injector by removing the spark plugs. Long-term fuel trim - a percentage of fuel change that effects the large portions of the map. 30 Apr 2019 . If the displayed fuel trim value is a negative number, it means that the ECU is decreasing the injector pulse width to subtract fuel from the . Ive been dealing with this sputtering misfiring for a very long time, I dont even remember what my truck used to run like. 22 Jun 2019 . Re: c5 rs6 high negative (partial) fuel trims. Compare 2021 Mazda CX-3 vs. This class is taken directly from Ron Bilyeu’s full course: The . 0 2x4 5 speed I have a misfire in 1 and 6 and both banks run lean. pressure test. Long term fuel trims now in -20 to -25 range. The negative persistent high Long Term Fuel trims mean the ECU is detecting too much fuel being delivered so it is adjusting the trim way into . The STFT is the decimal point of the fuel trims. Fuel Trim Diagnostics Using Fuel Trims during a diagnostic plays an important function in plotting a trend, be it either a RICH or LEAN trend. 7:1. This issue mostly occurs when the engine is warm, the acceleration is fine on a cold engine. The short term fuel trim on this car usually bounces between -2% and 8%. What remains the same is that fuel trim numbers increase as RPM increases. Driving a car with the code P0171 can cause more damage to the engine over time, as when the engine runs lean, the combustion temperature is higher. 0 ms or lower to correct for a hot-idle, excess fuel condition. Replied by Andy. Fuel trim should be checked at idle, at 1,500 rpm and at 2,500 rpm. 2019 Equinox LT 1. If the voltages you're seeing are accurate, the exhaust is very lean, and it doesn't make sense that the PCM is removing fuel (the negative numbers in the fuel trims). Fuel trims go into the+10 range only during acceleration. Under hard acceleration the engine controller can switch from closed loop mode to open loop mode and in this mode can fuel the engine for maximum power. 2086 182. « Reply #1 on: July 15, 2021, 12:05:58 AM ». 6. With Number 1 Cylinder Backfiring after accel over 3000 RPM. Each bank has its own fuel trim reading. Hit the gas pedal and no go. If i give throttle with the fan off, everything stays normal. Swapped the Fuel injectors t the other Bank. I previously noted that the fuel trims are different between the banks. When accelerating it's like there is nothing wrong but like I said idle sucks and highways speeds suck. Tested and checked IAC, TPS, and the coil rail. 2% acording to the Freeze frame data, also the vehicle was not moving as it was idling acording to the data. acceleration or load, we would see slightly negative fuel trims at . A negative fuel trim value means the engine computer is subtracting fuel. An oxygen sensor monitors the flow and generates a signal that is proportional to the oxygen levels in the. The intake, throttle body, etc were all cleaned and like new. Step 2 . Like the Forums. As its name suggests, LTFT data reflects the engine control system's overall trend adjusting the air/fuel mixture. Any thought. I have have been dealing with this P0171 diagnostic trouble code for many years on many different year make and model vehicles. Usually a valve timing issue on 1 bank will cause negative fuel trims as it does not breath as good. 2% and long term fuel trim 2 was -18%. Is the short term fuel trim now in the negative percent? Is the long term fuel trim returning closer to 0%? If Yes - Clear short and long term fuel trims by disconnecting the negative battery cable for 90 seconds. Offline. Short-term fuel trim happens as a result of changes in the oxygen levels of exhaust gases. Steady cruise at 60 mph and it would hiccup. When driving, it sometimes hesitates to accelerate and when holding a constant low speed (20mph or so) it will start to stutter and lose performance. I know this is a broad and common question but Im at a loss. log o2 voltages and ps_w. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. G8 with cam, no cats, LS7 MAF. Since the trouble codes indicate a lean condition (P0171 and P0174) on both banks of cylinders, both Long Term Fuel Trim 1 and 2 should be in their maximum positive number range as the PCM adds fuel to compensate for the perceived vacuum leak or failing sensor (whichever it may be). Short-term fuel trim - a percentage of fuel change that effects the current cel of the map you are in. . An excessively lean mixture can cause misfires. A Google search found links to OEMs (GM/Chrysler/Nissan) recommending a built-in filter change around 100k miles. What can also cause a negative fuel trim is the evap system malfunctioning, causing the engine to suck in more fuel vapor that it should. I have negative fuel trims. I also noticed that fuel trim values at idle had too much difference with about -7% total trim on bank 1. In this release we added support for a very impressive scan tool OBDPro. Long term fuel trims against engine rpm here. I recently changed the self learn to medium and then to slow, and my fuel trims are way out. Post Reply. If you're still on the factory spider at 320k then that's gotta be a record. So far I have about 250 miles with self learn on. I now see a rear 02 . fuel trim. My short term numbers are -. At idle the command goes to 0 and so does the vapor pressure. 11 Apr 2003 . Pay very close attention to the Long Term Fuel Trim values because they indicate how much the Powertrain Computer is compensating for an imbalanced air/fuel ratio. On our spring break 2000 mile trip this week, on the way back, with just 30 miles to go, I came to a stop sign. « Reply #1 on: July 15, 2021, 12:05:58 AM ». A negative long-term fuel trim means that the ECU has to decrease the injector pulse because the car is running rich. I also finally successfully performed a throttle body relearn, but the fuel trims are very high. Offline. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. The short term fuel trim value is greater than 1. The VVE is tuned, I just choose not to use it. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim. I have Ford fusion energi 2013 , and iam facing a bad fuel economy and a bad acceleration , I have conected my bluedriver to the obd port . When the engine is working hard accelerating or climbing a hill and needed fuel flow exceeds delivery, the fuel . Under sudden WOT acceleration close loop control is ignored. But you are watching the right things. 12 Mar 2017 . Adaptive Learning / Fuel Trim. STFT is used for immediate adjustments based on the parameters, whereas the LTFT is a slower adjustment. 0 A/F with iso- . my short trim normally fluctuates but thats normal. A/F is expressed as either a ratio (14. Large Negative Long Term Fuel Trim. Short fuel trim should remain near . Defining Fuel Trim. These cars are known for having bad purge valves if that valve stuck open you would be getting excessive fuel vapor in the engine. ) fuel density, 3. GM 3800 Service Tips, Techniques, and Advice. If the engine is running properly, fuel trims should be close to zero. 0 I know zero is ideal, but I guess I expected to see some minor single digit fluctuation +/- especially in the short term. But, If the vehicle has an external fuel filter it’s inexpensive just replace it. If the fuel system is open loop, 0% correction . The second component that has a negative effect on fuel mileage is the Exhaust Gas Recirculation Valve (EGR). The ECM/PCM will set the P0172 code in this case. Try to make this short. My short term fuel trim fluctuates about 5% positive to negative on idle. 3l. 7 lt ftrm1 % 3. Let off the accelerator pedal. Monitor your fuel trim at idle, if you engine is running lean your fuel trim is high. After 5 minutes of idling, the engine stopped by itself. Fig. The long-term fuel trim (FT) is a matrix of cells arranged by the RPM and the MAP. This happens because the PCM is supplying fuel for the amount of air the MAF sensor measured. Short-term fuel trims reflect the immediate demands of the engine, while long-term fuel trims are an . So I'd leave it, and the Fuel trims wander a LOT any way. In addition to these no-load checks, drive the vehicle at various steady load conditions and watch for fuel trim variation. ) timing failures. If you choose to follow any of these How-2’s, please do so at your own risk. This doesn't sound like a spark or timing issue so i'm thinking a fuelling or air issue. [report] [news] Friday 23rd June 2017. P0171 is a very common code for any ODB2 vehicle. The fuel trims will alter during the above conditions and their altering will provide leads on what is malfunctioning. STFT (short term fuel trim) is the instantaneous response of the ECU to reduce or add fuel to maintain an ideal combustion mixture. LFT was -28 to -25 at idle and around -10 while cruising. Joined Feb 11, 2012. #7. I checked all vacuum hoses through manual inspection. Negative fuel trim means the fuel mixture is too rich and the car's computer is cutting back on the amount of fuel it's delivering to the engine to . Fuel trim is a two-part adaptive strategy that adjusts fuel injector pulse width (open time) to adapt to wear, defects, or changes in the system. There is a cylinder 1 misfire pending code. The long term fuel trim is comparing the actual fuel trim (fuel pressure x duration of the pulse) to a table of theoretical values stored on a table in the computer that was derived from the engineers at the manufacturer. A MAF sensor would effect both banks. Joined Jan 2, 2019 · 151 . When the engine operates at normal or higher load or at higher engine speeds, larger volumes of fuel and air are needed. . So, picked up a second ECU to flash a stock tune (factory from scratch to be sure the "stock" tune in the car really was stock). Joined Jul 3, 2011. TEST 1: Fuel Trim Check. The actual fuel delivery during closed loop (engine warm) is determined by the O2 sensors, MAF, and other sensors. 202f On my way home from work today it felt like the engine was dropping out. fuel sys 1 clsd fuel sys 2 n/a o2s11 v 0. pressure test. At the same time it stops monitoring the converter performance, it ignores the #2 O2 sensor voltage readings. « Reply #1 on: July 15, 2021, 12:05:58 AM ». As for the mass air flow, it looks correct according to volumetric efficiency Chart but could still be an issue, I think you can unplug it and the car should run on a default strategy and see if that rear 02 comes down. The only time it's close to 0 is during accelerating. I also failed the emission test as HC and NOx were way over the limit. 13. A Closer Look at Fuel Trim. The car has 200,000km on it. Ford Fiesta P2096: Post Catalyst Fuel Trim System → Too Lean → Bank 1 March 1, 2020 by Jason P2096 is a generic OBD II code, which means that it has the same meaning for the Ford Fiesta as it would any other vehicle. PCM Rich Running. No amount of googling is helping. asked by. Fuel trim is the correction the PCM makes to try to maintain a stoichiometric air-to-fuel ratio. This is an emission control device that aims to control the emissions known as Oxides of Nitrogen (NOx). I know it's misfire with fuel cut off. When the MAF idle grams/second readings were highest, fuel trims improved. See Photo 3. Before that every thing was perfect. I assume those values are what set the Check engine light on. Short term fuel trim is also very good for diagnosing vacuum leaks. OP. A negative percentage means the PCM is subtracting fuel for a rich condition. Even for an experienced diagnostic technician, ­attempting to diagnose an intermittent misfire ­condition that occurs only under specific driving conditions can be a frustrating exercise. At low speed-load conditions, fuel flow is adequate so the fuel trims look normal. Furthest I've ever seen a spider make it was about 230k miles. Ignition coil faillure 2. This may be altered depending on the position of the . I run MAF only. All this happened when i added (STP fuel injectors cleaner 5-1). During this time the EGR, Purge and Fuel Trim diagnostics will be performed. I noticed that the long term fuel trims were in the -15 range. Car seems to be running rich on idle and had a look at the fuel trims with OBD 11. The long term fuel trim for bank 1 shows 6% at idle and 13% at 2500 rpm while the bank 2 long term fuel trim show 2% and 11% respectively. However, I was reading on how to interpret fuel trims and the readings are normally taken at steady rpms at idle, 1500rpm, 2500rpm, and 3500rpm held for 30s. This is called "Ignition Timing". I can make 8PSI on 89 WOT and not have nay KR but at 5" or so in second gear acceleration it pulls 3-4 but somtimes 10 degrees out. When the code says that the Fuel System is "too rich," it means that the computer has been subtracting more and more fuel, which is called Long Term Fuel Trim. Excessive negative fuel trims. With idling fuel trim numbers I'm already out of spec. The very first thing we'll do, to get to the root of the problem, is to see if the PCM is really seeing a chronic Lean Condition. In my case bad enough to set fuel trim DTCs and occasionally a DTC for the MAF sensor (which wasn't the problem, it was the throttle body). As we know, the general causes of a misfire fall under the ­general headings of 1. A negative fuel trim indicates the fuel is being taken away or being leaned out because the engine is running rich. pk (TuneUp Go) 2021-01-09 03:10:08 +0500 #8 Share the Primary (Bank 1 O2 sensor 1) data here. I have a 2000 A6 2. Negative Fuel Trims. 22 Dec 2020 . mikestony. After driving on the highway at 55+ mph for 10 mins no light. If the LTFT is negative, it means the ECU has been reducing fuel to maintain an ideal fuel mix. Recently I used some cheap 7/11 gas and my trims went whack and I could feel the power loss in my car. You must check them in all modes of operation. 22 Dec 2014 . Discussion in '2nd Gen Tundras (2007-2013)' started by Mosenzi, Apr 28, 2019. Answer. Bank 1 refers to the oxygen sensor on the number one cylinder of a V-6 or V-8 engine. Typically, code P0170 relates to a condition in which long term fuel trim requests cannot be met, meaning that when the requested trim value exceeds the PCM’s ability to adjust the fuel trim to the desired level by more than about 25% a code will be stored, and the CHECK ENGINE light will be triggered. The oxygen sensors show (bank 1 upstream) . 3 volts at 65 mph and . 0 Thx for all the help and replies. The short term fuel trim value on a scan tool is shown with a negative number. Due to high negative fuel trims, a leaking fuel injector will reduce average fuel injector pulse widths from about 2-3 ms to 1. 30 Jan 2013 . Thus STFT will read negative. The CEL came on and indicated a P0420 code so the first thing I checked was my O2 sensors and ended up changing out the up-stream sensor . However, when viewing the live data at idle today, I noticed the long term fuel trim to be -13. 7t with EPL stage 3 upgrades (RS4 turbos, 52lb EV injectors, 80mm MAF housing with hitachi sensor, cold air intake) and have their stage 3 tune that is adjusted to be stage 3 minus since I am running a TIP still. 4,342 Posts. Vehicle engines that are in good shape have around 1% to 3% Long Term Fuel Trim numbers, either positive or negative. Hello everyone, need advice on still trying to trouble shoot this problem with negative fuel trims and afr ratio I have 2 other threads . New question: On my scan tool, for the oxygen sensor, should I be looking at the reading from the Oxygen Sensor bank 1 (Reading 2-5v) or the "equivelance ratio (lambda)" Which is reading 0. At heavy loads or accelerating the trims seem to have less difference maybe 1% higher on bank 2 than bank 1. After servicing the transmission filters and fluid, I've got the car running and going down the road decently. 2,165 Posts. First, an air metering issue can sometimes cause slightly negative fuel trim numbers at lower RPM. But the longer I sit and idle the higher the long term fuel trim gets. 4L. 0. E="xler8er;2719398"]I know this is a bit old but this sounds like my problem to a t. MAF problems, MAP problems (though a non-turbo petrol engine usually has either a MAP or a MAF, not both, but there are exceptions), O2 sensor problems, fuel pressure too high, or injector problems can all give negative fuel trim. A negative fuel trim percentage indicates the PCM is removing fuel while a positive percentage indicates the PCM is adding fuel. Today I unplugged the MAF sensor, disconnected the negative battery pole for 10 minutes and started the car. 7:1 for example) or as a Lambda value. It also causes ping and engine knock if the valve remains closed. 2022 Nissan Pathfinder . but your wgdc is 95% up top which also points to a boost leak. Posts: 11644. This hesitation is most apparent in the 2000 to 3000 rpm range. Compare rankings and see how the cars you select stack up against each other in terms of performance, features, safety, prices and more. Unfortunately, this part is located in the fuel tank on most newer vehicles. Had a vac leak and IAC valve stuck open, LTFT was ranging between 11% and 25% at idle, no CEL. My main question of IS THIS NORMAL would only be answered if someone physically went out to their exact same 97-00 Civic EX and checked what there's is. Short-term fuel trims reflect the immediate demands of the engine, while long-term fuel trims are an average of short-term fuel trims. Positive fuel trims mean that the ECU is adding more fuel to maintain 14. Figured the MAF was shot. Originally problem was on Bank 1. Replaced the intake and exhaust actuators, cleared the codes, and have been good for a week. 27 May 2017 . 00 long term fuel trim for that bank reads at 11% However when I check bank 2 the o2 fluctuates the same way however instead of the line looking like a wave like it should it goes all the way up then halfway down the graph then all the . If fuel trim is negative at all speeds and loads check ect and iac. 202c I checked out the fuel trims while running and noticed they were in the high negatives. If the fuel trim numbers are more than negative -8, it confirms the engine is running rich. Mass Airflow (MAF) Graph and Fuel Trim Readings; Probable Causes: Lean Fuel (P0171, P0174) Throttle Position (P0120 or P0124) or (P0222 or P0229) An engine that hesitates, stumbles or misfires when accelerating or when it is under load, is an engine that is either sucking too much air, not getting enough fuel, or misfiring. Build 1. The short term fuel trim 1&2 was -2. I've got negative fuel trims at idle in the 5-10% range (moves around a bit, but that generally where the LTFT settles). A negative . Q: Extreme negative fuel trims only when coasting, with rpm bounce. The amount of fuel the PCM adds or takes away is a percentage and is expressed in short term or long term fuel trims. Positive fuel trims caused by leaking fuel pressure regulators and injectors also tend to disappear under increased engine loads. If you use a regular american OBDII scanner on a Mercedes negative LTFT mean the ecu is adding fuel vice veresa. Bank 1 vs Bank 2 indicates the side of the . 20 mins later the ses light came back on when I turned the car over only this time all the prior faults cleared except for p1439 - misfire cyl. The Long Term Fuel Trims can also be effected by the Fuel Pressure Regulator. Laredo 4. Jump to Latest Follow 1 - 20 of 22 Posts. 18 Mar 2020 . When this is happening the idle goes up to 1300 instead of the normal 750. The trimming or adding of fuel to the mixture depending on a feedback. Basically, a problematic engine has around 1% to 3% Long Term Fuel Trim numbers, either positive or negative. Truck has a rough idle. Reconnect the negative battery cable and test drive the vehicle. Technician A says if a lean condition caused by a vacuum leak, restricted injectors, dirty MAF, clogged fuel filter, or bad fuel pump exists, the LTFT will have a negative number. In this series of articles, we will review gasoline engine fuel control, otherwise known as fuel trim. Discovered Long and Short term fuel trim monitoring, . Look for vac leaks, find none. Ideally, the Long Term Fuel Trim should be close to 1 to 2 percent. 5t the ECU never set a DTC for the actual throttle body. Why? Maximum power is made between 0. fuel trim. Under sudden WOT acceleration close loop control is ignored. Awaiting new fuel pump assembly, just replaced dist with no effect either way. . 615/. 0 and show a negative value and then a positive value? Or does it stay consistently negative 7%? If so, check your long and short term fuel trims. In the May edition of “The Trainer” we explored how the ECM maintains fuel control. 12%) You see, fuel trim may decrease fuel to lean the fuel mixture or increase fuel to richen the fuel mixture. 07 Feb 2013 . but your wgdc is 95% up top which also points to a boost leak. Occasionally, the check engine light will stay on and . 11 Apr 2003 . Mid on/off: 75/62 High on/off: 156/144 That will give you three long term fuel trim values, just like the 1G guys. The engine in your vehicle is always switching between rich (negative fuel trim) and lean (positive fuel trim). Offline. On a V-style engine you can isolate which Fuel trims are now normal and the acceleration is much better. The trim seems to rise on acceleration but when throttle is released they start to drop again. The following is from p6-1156 Vol 3, GMP/98-Y-3 of my Helms Manual for the 1998 C5. 0 A/F with iso- . LTFT. My long term fuel trim is at about -7%. 7:1 ratio because there more air sneaking into the engine because of a vacuum leak. but your wgdc is 95% up top which also points to a boost leak. There are no DTC codes. - there are moments when I can't drive at constant speed (it's either accelerating, either . Does anyone know what may be causing negative and positive fuel trims? Thanks That down stream 02 should be steady 0. 08 and +. This should be providing petrol pressure in the fuel rail set at about 3 Bar. Is this PCM module properly programmed for the 42. Also his car was throwing any codes. If not so, then you have a leak in the fuel system It sounds like it could be a couple of things: 1. As soon as I went back to running my usual Phillips 76 91 oct with a little e85 (“California 93 oct”) my LTFT trim went back to around -3%. Recently got a P0011 code. So that is the opposite of a vacuum leak. 0 TFSI (EA113), A/T, gasoline, APR Stage 2+ tune What does it mean if you have positive fuel trims at idle (3-4%) and negative fuel trims under load/driving (-12 to -14%)? I need some advice. If the value is negative, it indicates that the ECU is decreasing the flow of fuel into the injectors because the data it sees shows that the . my car is running a little bit rich. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. It goes up to around 9-10% when the car is going up a hill or is accelerating lightly (20% . There is less oxygen in the exhaust B. It seems like the short term fuel trims can keep up sort-of in a lagging sort of way and the numbers tend to zero each other out after a few seconds, but it seems like LTFT goes as high as +16. The LTFT is the whole number. My gas mileage is poor. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. 92 Earlier this month we released build 1. At 2500 RPM, STFT and LTFT values fall off to around 6-10%, still not great. Trims were as bad as -15% for LTFT. Whats the fuel pressure when driving? You might want to hook up a gauge and see. If the fuel trim comes down chances are you have a vacuum leak. Mechanical Misfire Theory: MAF Sensor Placement! One of the major contributors to abnormal and erratic fuel trims, I believe, is Mass Air Flow (MAF) Sensor placement! So let's have a look at this interesting topic! There are four places you could possibly put the MAF Sensor when you add a turbo to your monster. 2 and it never changes. i have no catalytic converter. Hey there! Sorry to necro this thread, but I'm having the issue with extreme (relatively speaking) negative long term fuel trims to -35%, but, only after fueling up and driving off. Coils all OK. The fuel trim reading is 99. If the LTFT is higher than 10 either way, it may indicate a problem. What I've learned so far about the live data everything appears to be working correctly. Do not shift, touch the brake or clutch. 22 Oct 2014 . The LTFT might change. To start off, a technical description of Fuel Trims is in order. term trim went from -15 to -11 (at idle) directly following rapid acceleration. Fuel trim should be checked at idle, at 1,500 rpm and at 2,500 rpm. volume air flow sensor failed B. 4 V-6 tacoma, s/c. I have noticed that the long fuel trim for bank 1 and bank 2 on my truck show differences, when idling or at light load bank 2 doesn't go lower than 3. Re: c5 rs6 high negative (partial) fuel trims. . 11 Apr 2013 . Fuel Trims will increase in a negative going direction . Anyways I have not noticed any misfires, nor have I gotten any misfire codes. 186 months. w/ 120,000mi. It does not appear that the evaporator canister would be adding fuel when the valve appears to be operating correctly. If the Long Term Fuel Trim is over 10 percent on one bank of cylinders and not the other, there might be a vacuum leak or defective/cracked intake manifold on that specific bank. I have a 2002 EX-L with 82K miles. Then maybe a leak down test. The gauge could have bad calibration, or I could have a fuel delivery issue. Fuel trims will vary. The two parts of a computer fuel trim adaptive strategy are short term fuel trim STFT (additive) and long term fuel trim LTFT (multiplicative). This is typical of a dirty MAF sensor. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). Normally, the cycle will take between 1 and 2 seconds to go from low to high to low. And of course short term fuel trim (STFT) affects LTFT. 20b8 5 to 14. I am hoping someone would be able to get me some advice on tracking down a very negative long term fuel trim issue. This electric spark has to happen at exactly the right time or the engine will not run properly. Now the fuel trims will always be moving around a bit as you come on the throttle, hit a different load and so on, but for the most part they won't be crazy high. 8% Short term fuel trim is between -3% to 3% Mass. Rough acceleration 5 Answers. But the trouble codes only tell half the story. Fuel Trim Info. 8 to 7. . Thus making the computer pull fuel to try to keep a correct mixture. The LFTF value is stored in memory and "learns" from the STFT. Join Date: Feb 2017. In addition to these no-load checks, drive the vehicle at various steady load conditions and watch for fuel trim . What does this code mean anyway? The definition for this this P0171 code is Fuel Trim System Lean (Bank 1). I dont think the long term trim is fully set as well,to start with as it would be at 100% if it had run out of trim. XK8 / XKR ( X100 ) - Lean codes but negative fuel trim - I am . Positive fuel trim percentages indicate that the powertrain control module (PCM) is attempting to richen the fuel mixture, to compensate for a perceived lean condition. Negative fuel trim means the engine is running too rich, ie not enough air or too much fuel. The short term fuel trim (STFT) refers to immediate changes in fuel occurring several times per second. This happens when you tune a car incompletely. pressure test. I'm also getting engine pinging or detonation during acceleration . 95 Lambda (12. Installed a new MAF. Ideally, LTFT should measure 0%. Engine idles rough, poor gas mileage. O. When a vehicle rolls off the assembly line, it’s programmed to deliver the ideal mix of fuel for any given condition. Short Term Fuel Trim (STFT) is the computer’s immediate response to adjust the air/fuel ratio. At idle, LTFT goes back to normal when brake is depressed. All new fuel lines, vacuum lines, new pre-cat O2 sensor. to 26% and that's when accelerating with engine in Closed Loop. At idle you should see the STFT going positive/negative back back and fourth +or- 2-3. At idle bank one fuel trim is -20 to -29% (long term) and bank two is close to zero. 26 Jan 2021 . The fuel trims did go negative, to -3/-4 from +1/-1, so I decided the pump motor was fine. Car runs worse. You will see short term fuel trim go to a number lower than 0. Codes set since a few months: P0420 and P0171. When it’s positive the PCM will add fuel and when negative it removes fuel. If the LTFT pegs too high or low, the engine control module will set a code and take other actions to save the engine and catalytic converters. Each cell of the long-term FT is a register like the short-term FT. by Andy. and the exhaust does smell a bit rich. A negative fuel trim is considered anything at or below the minus 10 percent threshold. When the throttle suddenly goes wide open a huge gulp . No change. 8L Duratec, but it's not running quite right. STFT corrections represent the current engine run cycle and react very quickly to O2 sensor input. 1y. Posts: 37. Fuel trim isn’t something that can be read with an oscilloscope or meter – it must be reported to a scan tool by way of the datastream. Short Term Fuel Trim (STFT) -- The correction factor being used in closed loop by the PCM to maintain a balanced fuel mixture. The fuel trim chart on the left shows negative fuel trims at idle and positive fuel trims at cruising speeds. 11 Sep 2018 . -28 to -30 SFT at A dirty MAF sensor can cause this issue, but that diagnosis can be tricky. LTFT refers to changes in STFT but averaged over a longer period of time. Same on both banks. Long-term fuel trim - a percentage of fuel change that effects the large portions of the map. log o2 voltages and ps_w. to 0 the longer I accelerate but . If the displayed fuel trim value is a negative number, it means that the ECU is decreasing the injector pulse width to subtract fuel from the air/fuel mixture to lean out the air/fuel mixture because the input data it is receiving tells it that the mixture is too rich. Watching your air fuel ratio when it has sluggish acceleration would be better. I am going to have to do some research because I don't know what is good for fuel trims. Here are some common causes of negative long-term fuel trim: Leaky or chattering fuel injector Defective fuel pressure regulator unable to maintain fuel pressure or restricted fuel return line. If the closed loop sensors (MAF and O2) read that the system is running lean (less air means a higher AFR), then it will automatically subtract enough fuel to bring it back to the ideal air-fuel ratio as mentioned above. 670 st ftrm11 % -14. The -7 Fuel Trim brings the WOT fuel mixtures out of the ~11:1 range up in to the ~12:1 where it should be. Poor fuel economy / gas mileage; If you aren’t experiencing any engine or performance issues, you probably just had a bad sensor. A positive number tells you it's adding fuel. I also replaced one of the EGT sensors since the cable broke on it, the other one was fine and decided not to replace it. if you have access to a wideband try that. MISFIRE DTCS: A large intake air leak can also create a lean misfire and store a cylinder-specific P300-series DTC. Fuel pressure spec is 51 psi and the pressure should be > 29 psi after 30 minutes. When an engine is too rich all of the O2 the engine breathes is used up in the combustion process and for the catalyst to do its job, O2 has to make it to . If the fuel trims are better while on the throttle and trend positive at idle, that's indicative of a vacuum leak or faulty MAF. 7 parts air to one part fuel, or 14. 4% Long term fuel trim 1 was -17. key on engine off, 60--66 psi fuel pressure. At idle the exhaust gas analyzer shows the mixture at lambda 1. No Air or Vac Leaks. 781% Bank 1, -2. The O2 sensor will read this as rich, and the computer will lean out the mixture (causing negative fuel trim) to compensate. What makes checking this so easy, is that the PCM will let us know how Lean or Rich the Air/Fuel Mixture is with its Long Term Fuel Trim values (for bank 1 and bank 2). When the filter is badly plugged, you would on hard accel (during your 5 second hesitation) see the short term and possibly also long term go to +25 or even 30% or more. 6 o2s12 . Therefore the long terms are carrying over during wot. 01 Aug 2019 . Apr 28, 2019 at 3:23 PM #1 #1. This is done to LEAN out the fuel mixture to compensate for what it perceives as a rich running condition. LEAN DTCS: In general, a + 25% or greater fuel trim correction will store P0171/P0174 DTCs. this test engine was warm idling at 1k. Give it at least 2. Steady cruise at 60 mph and it would hiccup. This happens when you tune a car incompletely. The fuel trim chart on the left shows negative fuel trims at idle and positive fuel trims at cruising speeds. Just change the fuel injectors. It now has a new distributer and cap, fuel pump, fuel filter, new plugs and plug wires, throttle position sensor, maf sensor, egr and the problem is still present. D. You generally want these to be around 0, but +/- 10% is typically ok. A faulty (EGR) or exhaust gas recirculating valve results in stumble if it remains open at idle. MacFadyen. Try to make this short. Most engines (except diesels) use an electric spark to ignite a fuel/air mixture. If your scan tool can also display fuel trim data, look at short and long term fuel trim (STFT and LTFT). Jason S. Step 1: Physically inspect the fuel filter. I don't smell any gas, no Check engine light. 2,388 Posts. However, when we need acceleration, the mixture gets richer. 4 with fuel cutoff. If you have the spider fuel system, that system is noted for problems. This data was captured from a 2000 Pontiac GrandAm. As al ready suggested a WOT fuel pressure test (with gauge in sight) would confirm or eliminate the fuel pump. Change upstream O2. No Check Engine lights. If the car is running very rich (which is probably the case when the car is using this amount of fuel), you should be able to see this in the fuel trims. In approximately 40 seconds—or just before 54. 203d In the last year have changed spark plugs, coils, timing belt, water pump, pcv valve, maf sensor, throttle body, map sensor, power steering pump , and coolant temp sensor. On my way home from work today it felt like the engine was dropping out. This is short term fuel trim (STFT) at idle in closed loop operation. The fuel filter can cause loss of power, poor fuel economy, stumbling, hesitation, or even a no-start condition. After about 30 seconds of idling, they jumped up to +7. When you have temperatures above this point, NOx gases can be formed. Since the LTFT's are negative at low RPM, you appear to have an issue with air leaking out after being metered by the MAF's. If the fuel filter is dirty like the image on the right, it's probably causing a restriction of fuel flow to the engine and should be replaced. The Sense-Decide-React sequence continues throughout closed-loop operation, maintaining the proper air/fuel ratio. A negative trim would mean the ECM is SUBTRACTING fuel from the programmed rate. Think about it- If the engine's getting more air than it should for a given MAF reading (vacuum leak), it will adjust the trims up based on the O2 sensor readings to add fuel (keeping in mind the overall result may still be . Fuel Trim Background and Basics. Raise engine to 2500 RPM’s, hold and re-check. « Reply #1 on: July 15, 2021, 12:05:58 AM ». . 27 Jan 2014 . The short term fuel trims will drop significantly with increased accelerating, even going to zero or slightly negative when acclerating. Sometimes, I can feel the car "jerk" (as in car hesitated) when i throttle in or lift off throttle. I'm currently having trouble with poor acceleration and poor fuel economy. Down stream 02 decided to act all crazy (p0138) since I removed the cat. Ron addresses the common issues that can cause fuel . up to +23 or so. The more important data to observe is analyzing the long . Positive fuel trims caused by leaking fuel pressure regulators and injectors also tend to disappear under increased engine loads. But because all that air isn’t being supplied into the cylinders, the PCM is supplying too much fuel, creating a rich mixture. computer always opens injectors longer than 0 STFT, to get instant acceleration. The truck was recently tuned up with new plugs, wires, cap, rotor, and coil. Offline. S2000 Under The Hood - High negative fuel trims at idle - Issue still here. Short term was floating around 0. Posts: 11644. (D or R and/or when the AC is turned on max). 5. Most of us as technicians know that fuel trims are part of the ECM . Troubleshooting the P2096 code can help you find . Although an extended idle didn’t duplicate the failure, road testing indicated that B1 STFT varied slightly higher than normal — between -9% and +9% — while B2 STFT varied from -10% to +10%. -22 is significant and i am worried i might have some fueling issues. Short term fuel trims against engine rpm here. OBD2 Code P0174 Pontiac definition: Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). The oxygen sensor signal is a vital input for fuel trim in . Plugs new and properly gapped. 8 - 1. #2 · May 19, 2009. As a general rule, a maf sensor should report 1 gram of air for 1 litre of engine displacement, totally warmed engine at a low idle of 500 -600 rpm. LTFT refers to changes in STFT but averaged over a longer period of time. It seems to happen in open loop and when in closed loop the fuel trims balance out. And LTFT should be pretty stable at positive 7 or . That is not going to be a vacuum leak. Without the Enricher you should see negative fuel trims as the ECU removes the fuel added in boost. The LTFT is also influence by the Short Term Fuel Trim (STFT). So I've been playing around with my new Aeroforce gauge and I was surprised to see zero movement in both my long term and short term fuel trims (bank 1 and 2)-its pegged at 0. procedure is a more accurate means of diagnosingat idle (causes the fuel system to go rich) and the symptoms. The fuel pump is responsible for pumping fuel from the tank through pipes to the carburetor. Some of the most common Fault Codes (DTC's) pertain to fuel trim (rich mixture, lean mixture, etc. So, my check engine light is on for (only) P0171 and I do have some hesitation under acceleration. Dealer indicated the O2 sensors were good. Discussion Starter · #1 · Apr 1, 2012. No check engine light is on so I'm having trouble finding it. It is NOT a rich or lean reading. 7:1 air/fuel mixture ratio. If LTFT or total fuel trim is more than 10% negative, the PCM thinks the air/fuel ratio is too rich, so it is leaning out the mixture calculation to return STFT control to the correct range. If you have not already started tuning everything, set your overall fuel trim back to 0% and then tune. Okay, next issue. Warm idle shows a -6 to -8 % long term fuel trims. With the Enricher activated and correctly set, you should see no net change or positive fuel trims in boost. 30 Jan 2019 . If I look at my scanner the fuel trims will suddenly go negative up to - 20 and then the engine smooths out. Its got enough pressure and volume at idle but under acceleration its dropping the volume out and hence the - fuel trims. looking at your data file, bank 2 is going lean under load as you accelerate. When i release the throttle then LTFT go to -13% or -14% There is a smell for fuel in engine oil I think i have leaking injectors. But negative fuel trim means the computer is forcing the air/fuel mixture leaner — reducing the fuel within the mixture. Also check the voltages on Bank 2 . The car is running rich. Zero fuel trim would (theoretically) be a perfect LTFT. My car has been running great for a few months now with the self learn in fast. I have a 97 3. . Fuel Trim constant negative. sounds pretty normal to me. Be sure to consider what kind of fuel you run too. * Negative fuel trim values. LTFT refers to changes in STFT but averaged over a longer period of time. I know it is not an issue yet, I'd like . New cat gets put on next week. Re: c5 rs6 high negative (partial) fuel trims. If your scan tool has ability to graph, check that way. Did Forscan list a Rear O2 Fuel Trim in the PCM data list? Probably not, given the model year, but it might be fun to check. Troubleshooting DTC code P0172 – Long Term Fuel Trim Rich. Differences smaller than about 25% . He said normally it should only vary in the positive or negative single digits. If it was tuned that way, leave it alone. Air Fuel Control The Stoichiometric mixture of 14. If you create a vacuum leak, O2 voltage will go low. If your engine is running excessively rich (too much fuel) over an extended period . A negative fuel trim indicates the fuel is being taken away or being leaned out because the engine is running rich. A positive fuel trim means you are using the ECU to help add fuel in boost. If it is dirty, the fuel trim will remain normal (within 3 to 5) at an idle, but when you reach 2500 RPMs, the trim will go up 5 or more into a positive range. 04-02-2021, 11:53 AM. Think of it like this: You're driving from the beach at sea level into the . If fuel trim is over 10% (positive or negative) you This was second clue about possible fuel delivery problem. Exhaust Leak find via Soapy Water and leaf blower. December 27th, 2017. The system seems to work great so far but the app keeps staying at -29 on long fuel trim when at light throttle/cruising and short fuel trim is usually at 0 but the afr . This thread is interesting to me. If fuel trim is negative low speed and load, look for fuel pressure regulator or injector leak. After the test drive, proceed to step 5. Accelerate. I've looked at my fuel trims and Bank 1 was is on -25% and Bank 2 was on 27%. Short term fuel trim If the O2 swings high (rich) and stays there, the fuel trim will respond by beginning to correct to the negative side of zero and continue to correct until the O2 sensor indicates that the negative correction has returned the O2 sensor to normal activity. 2011 New sensors like MAF, MAP pre, MAP post, air charge, etc. A negative fuel trim is considered anything at or below the minus 10 percent threshold. The 'issue' (and I'm not sure it really is one) is that my LTFT is still fairly negative and I cannot figure out why. Did you reset the fuel trims after replacing the fuel pump? Maybe the system is still using the old long-term fuel trim values, which would explain why they are negative (since they were previously positive). sometimes negative, but mostly positive. If it sees extra oxygen, it has to add fuel to burn that extra oxygen. Only code BTW. 08 to 1. Discussion Starter · #1 · May 7, 2014. However, some run high, like five percent. Positive fuel trims should add fuel, . I get codes 1-2-1 (Faulty signal to/from Air Mass Meter), 3-2-2 (Air Mass Meter wire burn-off signal absent or faulty) and 2-3-1 (Fuel trim (lambda control) too lean or too rich at part load). The Short term fuel bank 1 and 2 get pinned to +25 and long terms stay at +5 and +6 When this is happening, If i give it throttle, the fuel system goes to Open Loop and the short term fuel trims goes to 0 and the car starts to hessitate. I was gently accelerating to about 50 when I got the “restricted . 85 to 0. When a code P0172 is set, it means that the Fuel Trim is anywhere from -15 percent to as low as -30 percent compensated. Add a comment. Jan 24, 2013. Not matter what rpm it is at. 0 ms or lower . If the O2 sensor says the exhaust is too rich (too much fuel) the ECU will reduce pulse width of injectors to subtract fuel. . Build a strategy that is reliable and you can trust. Negative fuel trim value, contrary to positive one indicates there is either too much fuel or too little air goes to only one bank of cylinders. ) ignition, 2. If you see this generic code, it’s likely a problem in the exhaust system. When the throttle suddenly goes wide open a huge gulp of air enters the inlet, the pressure in the manifold rises close to atmospheric, the mass of air entering each cylinder increases, the compression pressure increases as a result the engine computer has to compensate very quickly. From my. Where im confused is that the low fuel pressure 43 is consistent which i would tend to expect a lean condition? Since its rich -18 at idle but resolves quickly with any acceleration AND has no issues at full throttle, im thinking diaphragm or spring defect or something else with the fuel pressure regulator is keeping the fuel pressure regulator-controlled fuel return line open (instead . Negative (Rich) Fuel Trim - Long Term Fuel Trim Very negative fuel trim @ idle (close loop, operating engine temps, etc). It also runs negative @ cruising speeds (between -10 to -15). If long-term fuel trim (LTFT) for bank 1 is 25% at idle, but corrects to 4% at 1,500 and 2,500 rpm, focus on factors that cause a lean condition at idle, such . Fuel trims, Around Negative 18. When the car is Idling it shows 6. Decelerate. Going back to our stoichiometric ratio, which is 14. Both of my primary O2 sensors are new Bosch universal sensors replaced 2k miles ago when I put in my K04s. 8-4v+ volts on AF sensor). You might have a pump starting to fail. Excessive Negative Fuel Trim Bank 2. a wired acceleration problem i have experiencing is when i floor gas pedal car accelerate really good a while after this acceleration is not good as before and like . 182. 3 voltage when this happens. Here are some common causes of . « Reply #1 on: July 15, 2021, 12:05:58 AM ». changes to fuel trim on a scan tool. CAT temps run at 1650 when driving. 2 eng speed rpm 435 calc load % 98. However, when we need acceleration, the mixture gets richer. The MAF sensor overestimates airflow at idle, which causes the negative fuel trim values. but your wgdc is 95% up top which also points to a boost leak. This signal is used to indicate normal and sudden acceleration. 2%: Long Term Fuel Trim: Similar to short term trim, long term fuel trim reacts less readily to sudden changes and represents the 'learned' behaviour of the vehicle over a longer period. 2003 XLT 4. Now we talk about the myth: "learn-around" is caused by constantly changing long-term fuel trims. . Re: FUEL TRIM. update:it was fuel pump that solve problem completely -----hi everyone. Hey guys, I have the ProFlo 4 setup on a 331 sbf with the "race cam" setting. If you’d like to learn more about fuel trim in general, read this post. A leaking fuel injector could cause a rich . PCM will command a rich command. Need some help. pressure test. The long term fuel trim maintains at -2 to -3% fuel trim. would be fuel maps of Short Term and Long Term fuel trims or Ignition timing maps. Only thing I can see that's possibly out of the ordinary with my limited knowledge of it all is the long term fuel trim 2 is always positive, and never goes negative like the other long term trim does. 81/8. 8 map kpa 98 coolant f 170 iat f 80 ign advance de -1. If it was reading that high while cruising or accelerating, . The fuel trims will react with a negative value. I replaced the plugs, noticed two from. 7 o2s12($10) ---obd2 stat ca frame 6 time 20. Let's begin by getting the basics out of the way. 781% and 3. Positive fuel trim means the computer is adding extra fuel (too lean). at 2,500 RPMs, it is likely there is a fuel delivery problem (clogged filter, low fuel pressure, restricted injectors, etc. 0 liter engine. Kept pressing all the way down, then slowly acceleration picked up, but around 40-50mph, car was shaking erratically as if engine was having trouble breathing. The general consensus is that if the fuel trim values are within -5% to +5%, then the sub-60-g/s (closed-loop) region of your MAF scaling is good enough. The neutral value for the short term fuel trim is 0%. On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn’t have cylinder #1. Closed loop is when the ECU is using an O2 sensor to get an air/fuel ratio reading from the exhaust to determine whether the motor . 002 and 14. LTFT for bank 1 are pretty much 5% all the time, with LTFT for bank 2 at 3% all of the time. Fuel Trim Short term fuel trim bank 1 sensor 2. (Series II and III engines. On my 1999 chevy silverado with the 2005 front clip conversion it started sputting and having a random missfire upon acceleration at times. 6 seconds—STFT begins to move in a positive direction, and within about 14 seconds, no fuel vapors are being purged from the charcoal canister. 2005 Infiniti G35 Coupe Fuel Trim Too High. Re: Knock retard and negative fuel trims Ive been fighting a mid throttle knock also. ) compression and 4. Everytime I turn in the car on it's coming to similar values after a while. O2 sensor is toast/gamble on a junkyard sensor. While accelerating, it feels like the power is "slipping" away from the accelerator; when I'm idling, the car is shaking in waves (coming and going) while the RPMs increase and decrease ~500rpm--idling is rough. 送料無料 北欧 デザイン チェア おしゃれ モダン 。MENU Flip Around スツール When idling, trims just go way negative and then once warm, the jerking and hesitation occurs. I have Big fuel trim issues and now everything is moving,sweeping as it should . This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows. S-Series Tech. What could cause the PCM to subtract fuel from only one bank during a misfire? A rich biased O2 sensor may cause inappropriately negative fuel trim on one bank, resulting in a lean misfire. 13. , on, off, on, off, then stays off). . but your wgdc is 95% up top which also points to a boost leak. Repair-ing the issue will often cure the converter code. Therefore, negative fuel trim makes it much more likely that fuel trim is causing the misfire than reacting to it. Fuel trims of plus or minus 10% are considered normal, while plus or minus 25% . 9% and long term Fuel Trim 1 was at -17. It subtracts or adds 1 to the LTFT. 0