What Causes Negative Fuel Trim At Idle

A rough running engine. FUEL AND IDLE CONTROL VALVES FUEL CONTROL VALVE (FCV) An electrically actuated control valve used to trim off idle fuel mixtures by controlling the pressure on top of the regulators secondary diaphragm. To put this into perspective, lets say at WOT we have a LAMBSE of 0. to relieve negative torque conditions, the plunger retracts and the propeller returns to normal operation. A bad fuel pressure regulator can lead to a build-up of excessive gasoline that can lead. At speed this keeps bow down and more of boat running surface in water. Has been great vehicle. It uses fuel trims for this purpose. If the cause of the current DTC cannot be determined and the DTC P0300 is also set, refer to DTC P0300 Engine Misfire Detected. P0171 BUICK Meaning The Engine Control Module controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Flashing check engine light or malfunction indicator lamp in the vehicle?s dash board. Fuel delivery, fuel condition, and fuel volatility are an important part of today's vehicles. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance. Disconnect the EVAP line and put your finger over the purge valve port at idle, there should be no vacuum. Then activate each fuel injector and look for a consistent pressure drop. 96 at idle and 1. To be safe and make sure the process works. This first article I’ve started at page 3, just so you’re aware. 6 then by 1300 rpm all is perfect This truck runs perfect, no warning lights, just playing with my fuel trim data What would cause bank one to run rich at idle ONLY ON LTFT DATA. Issues like leaking fuel injectors, a defective fuel pressure regulator and defective MAF sensors will be addressed. At 2500rpm with no load, LTFT goes to +5%. 6 and tooling around generally flopping between 14. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. LTFT near zero). Of course this can happen for other reasons as well (and a defective oxygen sensor is one of them!). Incidentally, the negative fuel trim response indicates that the ECM is attempting to compensate for what it believes is a rich mixture. Using negative split (firing trailing before leading) at idle and light load can result in emissions and fuel economy increases. The fuel trim data can be displayed as a percentage, either positive or negative. Good for our health and enviroment. 3000GT/Stealth Fuel Trims By Jeff Lucius Below is a summary of what we know about Fuel Trims in our 3S cars, as I understand it. When you see 5-10 turn vehicle off for 30 seconds this will reset tps. Am guessing this is the cause of the rich running, but not sure where to. As Nick mentioned, you will need to check across the range to see when the fuel trims go out of spec. the car is too rich and the PCM is attempting to ‘trim’ a percentage of fuel out. The short term fuel trim 1&2 was -2. It’s running rich according to the oxygen sensors. There are many things that can cause these codes. Transversely if the number is a negative number above -10% then the vehicle is running too rich. On hand held find "IAC STEP" adjust idle screws (both sets) 1/8" to 1/4" turn equally until IAC STEP is 5-10. A dirty MAF sensor can cause this issue, but that diagnosis can be tricky. 6 shows fuel trim and volumetric efficiency charts related to the MAF sensor. If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. That's basically the EFI equivalent of a choke that won't open- an ECT that is reading much lower than it should will cause the PCM to fuel as it. The pre-catalyst exhaust gas oxygen sensor is the primary component used for calculating the fuel trim once the system enters closed loop control. Install the outboard motor at the best trim angle for stable cruising and maximum power. What are the causes of negative fuel trim? I recently was having a problem with high positive fuel trim at idle and suspected a vacuum leak. Common causes of a mechanical misfire are worn piston rings, valves, cylinder walls, or lobes on a camshaft; a leaking head gasket or intake manifold gasket. A defective O2 sensor will likely cause your air-fuel mixture to be too rich and directly affect your fuel economy. In the "Old" days, that was a stuck choke. long periods of idle time can render a non-heated or older o2 sensor too cold for it to function at all. I would be grateful if you or anyone else could shed some light on the actual numbers I posted, the measurement units, their meaning and especially numbers from the same data points on Boxster motors in tip-top. Once the long-term trim is in place, the short-term continues to operate and go positive or negative as needed … past the standing long-term trim. An increase (positive) means there is excess (unmetered) air, like a vacuum leak. Allow the engine to idle for at least one minute. Hi to all! Due to some drivability issues I've decided to verify/diagnose my Mazda 3 engine's management (1. The LFTF value is stored in memory and "learns" from the STFT. Idle Speed Error" Zero out that map! Then the timing won't change. Your car engine will absorb more fuel than regular. In other words, there will be more air entering the engine than is needed to balance out the air/fuel ratio. Couldn't tell you why, it would be nice if Honda just left everything the same. When the air/fuel ratio is less than 14. On late model vehicles with computer engine controls, the engine management system will detect any changes in the air/fuel mixture and compensate by increasing or decreasing short term and long term fuel trim (STFT and LTFT). Truck has a rough idle. Typically, fuel trims will be within 3% of the ideal, dependent on current air and coolant temperatures and load, for example. 7:1, lambda also is less than one and the engine has a rich fuel mixture. A positive fuel trim value indicates that the PCM is adding fuel in order to compensate for. To check for a VAC leak, log block 032 and check the idle fuel trims. The fuel trim chart on the left shows negative fuel trims at idle and positive fuel trims at cruising speeds. I estimate the lambda to be about 1. CPOed 6 months ago. Turn the tester on. Answer I have just recently started having misfire issues with my 2000 with a 3. 32, then odds are you have a bad AMM. The fuel tank pressure sensor measures the positive and negative pressure in the fuel tank. For example a air leak at idle with no loads will cause high oxygen content in. Vvt gear, timing chain , vvt solenoid, and chain tensioner were changed. The ECU is doing it's job, no worries there. The only symptoms are sooty exhaust and high fuel consumption (27 mpg even taking it very easy on the motorway), and a. If the air is not measured by the MAF then the fuel will not be injected. Remove the negative battery cable for 10 seconds to accomplish the reset. but should not cause a high idle. Cummins ISC 8. Once I start driving ,however, both the STFT and long term fuel trim approach normal limits (i. underestimates the air which causes a lean condition IF THE FUEL TRIM IS _______ AT IDLE YET ITS ADDING FUEL AT HIGHER RPM, THE MOST LIKELY CAUSE IS A _______ MAF -NEGATIVE. 4L (RPO LUJ or LUV). A bad fuel injector restricts the flow of fuel into the engine cylinder, which will greatly decrease the force of combustion which will later cause either a coarse engine idle or misfiring. By the way, I think your car does have a MAF. predator the fuel trim at idle now looks much better ( long & short ) What I've noticed is when driving lets say 50 or 60mph and the light up ahead turns yellow and I let off the gas to coast up to the light the long term fuel trim spikes from anywhere between -3/-13 to -22/-26. Only then, should you use this map to make it even more perfect! Try a richer AF. Modern Air/Fuel Ratio Sensors can be difficult to test and inspect. The reason I think that a leaky injector would cause a positive fuel trim instead of a negative one is because the seal on the bottom of the injector would be a little easier to break (less system back pressure) so the fuel pump will have to supply more fuel to the injectors to compensate for the lack of back pressure in the fuel system, hence positive fuel trims. The fuel screw setting at idle trims the pilot fuel, and considering the fuel screw ends up at 1. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle. A fuel trim of 0% is perfect, but unrealistic, some amount of trim should always be expected, and even required for proper vehicle operation. Also getting p0174 have replaced fuel pump and filter which wasn't bad and smoked engine and no negative results. Venture Effect: Negative Pressure Pulses Thinking some more about this: The valve is supposed to keep exhaust gas back-flow into the secondary air pump and thus fouling & frying it. We asked the shop to perform a fuel trim test once again, and the engine was still lean. If it is more negative than -12%, the fuel system has learned lean corrections which may be due to the MAF sensor over-estimating air flow at idle. Fuel filter has about 14,000 miles on it. When certain conditions have been met to begin learning fuel control (ECT, closed loop, etc. What are short and long term fuel trims at idle and 2500 rpm on each bank? Total fuel trim values are short plus long term as long term fuel trims goal is to keep short term fuel trim as close to zero as possible. 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. 0 in the short trim. The MAF is reading 15g/s at idle which i believe is high, should be around 3g/s?. Generally this indicates leaking injectors, excess fuel pressure or a regulator leaking fuel through the vacuum line. Watch fuel trim (%) for a large shift into the negative (-) range (due to a rich condition). If you experienced the second result, you probably have too much Base Running Airflow added (Airflow Final Minimum table). This happens because the PCM is supplying fuel for the amount of air the MAF sensor measured. There could actually be too much fuel going to Bank 1, but -35 percent fuel trim is still considered "in fuel control," so the engine should be running well. Disconnecting the MAF sensor or using a scan tool can clear a learned value. Sudden decrease in fuel mileage. The volumetric efficiency was checked to confirm the diagnosis. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. Small corrections cause no problems, but large corrections (more than 10 to 15 points negative or positive) will typically set. fuel; a negative percentage, subtracting fuel. in the engine. Leaving it idling actually can be detrimental, and it wastes fuel, which causes a negative environmental impact as well. Target idle speed is compared against actual engine speed to determine the learned TPS value for closed throttle idle. During periods of idle or trolling, trim the engine up at least half-way so the "heavy ends" of fuel and oil will reaach the recirculation system. That being said, there is nothing alarming about an LTFT of negative 8-10 percent. Idle Issues- With the air/fuel mixture altered, the vehicle can idle erratically as the computer compensates to keep the engine running.  Tests/Procedures:  1. 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. At 2500rpm with no load, LTFT goes to +5%. When you see 5-10 turn vehicle off for 30 seconds this will reset tps. A fuel trim of 0% is perfect, but unrealistic, some amount of trim should always be expected, and even required for proper vehicle operation. See the map called "Spark Offset vs. The long term fuel trim makes coarse adjustments to fueling in order to re-center and restore control to short term fuel trim. Open Loop-Drive Heavy Acceleration Noted Negative Fuel Trims • The system is subtracting fuel for a perceived rich runninga perceived rich running. LTFT Info. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. What Does the Trouble Code "P0172 System Too Rich" Indicate? Credit: John Millar/The Image Bank/Getty Images The trouble code "P0172 system too rich" means there is too little oxygen in the exhaust. Conversely, if. In the "Old" days, that was a stuck choke. While it will most likely occur while idling, it is not unheard of for the car to stall while you are driving down the road. My 2wd 2000 Honda CRV with automatic is showing rather large negative adjustments to the short term fuel trim (STFT) at idle. Prime the fuel rail by turning the key to the ON position for 2-secs. The primary fuel enrichment is a multiplier (determined primarily by the open loop fuel maps) applied to the base injector duration to determine the level of primary enrichment. 17) Check for Oxygen (O2) sensor function tests. Clogged fuel injector port. When the feedback from the HO2 sensors shows a deviation, the PCM adjusts the amount of fuel the injectors deliver, in an effort to hit the stoichiometric goal. Long Term Fuel Trim Description. Short term fuel trim (STFT)is quick changes to the injector pulse to correct fuel mixture, and long term fuel trim (LTFT)is for continuous steady changes. Hence the AOS can cause a lean running condition that can affect the fuel trim values but without any other symptoms. The fuel trim has two means of adapting; Long Term Fuel Trim and a Short Term Fuel Trim. It can be the switch, but that seems to be rare. The LTFT works to bring the STFT close to a 0% correction. The STFT pre-cat drops to about 1% at engine warmup. Cold Start Rough Idle So, my 7mgte just randomly started to cold start rough and after warming almost seems to miss fire every once in a great while, though after it warms up the roughness go away. Also, look for black soot at any point in the system as this can indicate an exhaust leak. Once the long-term trim is in place, the short-term continues to operate and go positive or negative as needed … past the standing long-term trim. It then underestimates airflow at cruising speeds, which accounts for the positive fuel trim values. (00068a) Connect the battery cable, positive (+) cable first.  Tests/Procedures:  1. A positive fuel trim value indicates that the PCM is adding fuel in order to compensate for. Hey there, thanks for writing in about your 2000 Lexus ES300 Your car has what is called an idle control valve, which regulates the flow of air into the engine while the car is idling. In hot weather when the air is warmer the amount of oxygen atoms in a given volume of air will be less that in cold air. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. At idle speed, the engine generates its lowest emissions, thus conserving fuel. Cummins Accumulator Pump System (CAPS) fuel injection pump for Cummins 6 cylinder C series engines where used in heavy duty on-road, agricultural applications and many Motor-home applications. Check fuel pressure and stuck injectors. Sometimes, the engine will misfire on idle also; your engine sensors will get faulty values, and the air-fuel mixture will get messed up. Idle about 9500-950 rom. but still it's worth checking out. Subject: Possible Oil Consumption - Oil Leaks - Blue Smoke From The Exhaust - MIL - Or Fuel Trim Codes Models: 2011 - 2014 Chevrolet Cruze 2013 - 2014 Buick Encore 2013 - 2014 ChevroletSonic 2013 - 2014 Chevrolet Trax (Canada Only) Equipped with 1. The Idle Air Trim values are stored in a table for reference. While diagnosing an idle speed problem: Technician A says that higher-than-normal TP signals at idle will cause the IAC to close, which will decrease idle speed. Engine Adaptation Values. IAC- Hot start issue, high or hunting idle. Remove the battery from the boat before working with fuel. I would strongly suggest doing some routine maintenance to your ski. A rough running engine. If your trims are increasing, add more to the VE table in that range to bring them back to 0. The LFTF value is stored in memory and "learns" from the STFT. Drive the vehicle at least 12 mi (20 km) to completely relearn the idle and fuel trim strategy. Negative torque caused by the airflow going faster through the prop than the prop is pushing is dangerous. Note that both Banks 1 and 2 will exhibit negative corrections for 2-bank system. Idle air control valves and dirty throttle bodies can also cause idle problems like this. Two new fuel rail hose connector o-rings GM PN 14104675 (discontinued by GM) will be needed as well as two plenum gaskets GM PN 10168684. Often high negative fueling corrections are a function of one or more of the following conditions: 1) high fuel supply pressure to the fuel injection system, 2) a non-responsive HEGO/UEGO sensor, and/or 3) an injector that is stuck open. Is this right? MAF reports 2. The DROOP range is adjusted with the DROOP potentiometer. The fuel pump relay is also used to turn on the injectors, and will show injector short to ground.  Tests/Procedures:  1. 8 at 800 rpm, once I rev slightly it goes to. Then look at the freeze frame data to see which one of these fuel trim levels failed and under what conditions. This figure varies from 2. The only difference between open and closed loop, is that during close loop the ecm is monitoring the O2 sensor, to trim the air-fuel ratio to 14:7. Two new fuel rail hose connector o-rings GM PN 14104675 (discontinued by GM) will be needed as well as two plenum gaskets GM PN 10168684. The negative value fuel trim means the engine is running rich at that time and removing fuel (negative value). Pretty neat feature I should say, but then discovered a potential problem. When engine RPM was raised (off idle) short term fuel trim dropped to a normal range. Changes in o2 sensor voltages cause a direct change in fuel. You can use a scan tool in order to monitor the short and long term fuel trim. If the ECT was the cause of your rich condition, you would see grossly inaccurate readings while viewing sensor data with a scan tool. What remains the same is that fuel trim numbers increase as RPM increases. Scan the LFT and Barometer (BARO) sensor readings. From the tank, there is a feed line that runs through the fuel filter and up to the fuel rails, which supplies the injectors with fuel. Test by attaching a fuel pressure gauge. Prime the fuel rail by turning the key to the ON position for 2-secs. 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. Idle air control valves and dirty throttle bodies can also cause idle problems like this. One or more of the PIDs are out of range when compared to "known good" values. You can also watch the fuel trims under a load too. Fuel delivery is controlled differently during Open Loop and Closed Loop. predator the fuel trim at idle now looks much better ( long & short ) What I've noticed is when driving lets say 50 or 60mph and the light up ahead turns yellow and I let off the gas to coast up to the light the long term fuel trim spikes from anywhere between -3/-13 to -22/-26. 3000GT/Stealth Fuel Trims By Jeff Lucius Below is a summary of what we know about Fuel Trims in our 3S cars, as I understand it. Long-term fuel trim (LTFT) is the slow rectification in the fuel trim by the engine system. Circuit Description. Looking at previous posts the fan on my mini is either full on or not at all. A poor fuel pressure regulator can also cause your Ford to stall while idling or driving. P1503 Load Signal From Generator Range/Performance. Short term fuel trim will see the high voltage from the O2 sensor and command a lean correction. Jump to Latest Follow And, a vac leak tends to make things go lean with unmetered air which would normally lead to a positive fuel trim. They removed a lot of extra junk, mainly for EVO's, but added items to log even more features. 96 at idle and 1. Whatever is causing the high negative fuel trim needs to be figured out. START FUEL DROOP% FUEL RAMP. 1) Possible causes. Assure there are no vacuum leaks then go. · Idle control valve sometime sticks open - causes issues when in Idle. An increase (positive) means there is excess (unmetered) air, like a vacuum leak. Code P0172 Common Diagnosis Mistakes. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. A little is fine, too much and you get a code. Prime the fuel rail by turning the key to the ON position for 2-secs. But these corrections may only be necessary at idle; not at cruising speed. While diagnosing an idle speed problem: Technician A says that higher-than-normal TP signals at idle will cause the IAC to close, which will decrease idle speed. 75, which is far far too high. Misfire– If the air fuel mixture has gotten too far from factory specs, this can cause the Yaris to misfire. Overtime I check the trims I add them to the base table and eventually it brought my idle VE value as low as 28%. Cold Start Rough Idle So, my 7mgte just randomly started to cold start rough and after warming almost seems to miss fire every once in a great while, though after it warms up the roughness go away. Remember, all this is based on what the oxygen sensors are telling the engine computer. Before servicing any part of the fuel system, stop. Many fuel system and emission components have a direct effect on the air/fuel mixture ratio. Conversely, if. If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. I have no new codes but a slight hesitation when I get on it. This causes the fuel trim numbers to become negative during a boost situation.  Tests/Procedures:  1. Idle Issues- With the air/fuel mixture altered, the vehicle can idle erratically as the computer compensates to keep the engine running. This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows. Some common causes are: MAF malfunction, incorrect signal information sent to the ECM Low fuel pressure, faulty fuel pump Unmetered air leak, such as torn intake boot, etc Pressure regulator malfunction Excessively negative multiplicative adaptation values indicate rich condition. 89 octane is good to use if the engine is run infrequently. It requires a larger leak to drive the Fuel Trims high enough to set a DTC. A bad MAF sensor will tend to have positive fuel trims at load. Fuel delivery, fuel condition, and fuel volatility are an important part of today's vehicles. The system (engine control unit) does not “foresee” any fuel corrections. Currently the only code on my 2002 dakota quad cab is p0441 which is incorrsect purge. It seems this stumble is occurring when on the pilot 100%. 32, then odds are you have a bad AMM. You can see signs of high exhaust back pressure on a scan tool; calculated load will be low at wide-open throttle (WOT) and fuel trims will trend negative as engine speed increases.  Tests/Procedures:  1. Many people will replace the air-fuel sensor or O2 sensor as soon as they get a bad reading, but the root cause is often a dirty or faulty Mass Air Flow (MAF) Sensor or vacuum leak, thus causing the O2 or A/F sensor to read. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. Took it apart and cleaned it. The ideal fuel trim values are around 0 percent. There are two types of fuel trim – short term (STFT) and long term (LTFT). I'm with you though, I don't know if a spark plug occasionally not firing would effect anything enough to cause the PCM to make a. STFTs are used at idle and part throttle. Edit: Replacing the MAP sensor (which was suspected to be somewhat out of calibration on lower pressure readings after doing a vacuum gauge check) seems to have fixed the lean idle. When the fuel pump relay goes bad it will trigger many fault codes with electrical shorts to ground. Has started slow return to idle when take. Long-term fuel trim is a Self-Learned value. AT THE SAME TIME, DO NOT TRY TO FORCE A HEATED O2 SENSOR INTO OPERATION. Late Model Hondas and High-Tech Diagnostics A leaking EGR valve may cause negative fuel do not see the Fuel Trim change with EGR leaks. Overtime I have checked the fuel trims it has maxed out its negative trim on one bank and typically the other bank is around 5-10%. The NTS system functions in flight during temporary fuel interruptions, air gust loads on the propeller, normal descents with lean fuel scheduling, or high compressor bleed-air conditions at low-power settings. So what next? To answer this question, consider what makes a diesel engine tick. Negative torque caused by the airflow going faster through the prop than the prop is pushing is dangerous. I have no new codes but a slight hesitation when I get on it. Idle Issues– With the air/fuel mixture altered, the vehicle can idle erratically as the computer compensates to keep the engine running. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. Once this bend in the hose rots and causes a vacuum leak many performance problems crop up – loping engine, lean miss, stalling, high idle speeds, hesitation, power loss, and the PO171 & PO174 code combo. but still it's worth checking out. Negative fuel trim means the ECU thinks the motor is running rich and is removing fuel. 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. to your engine backfiring or the smell of fuel when you decelerate your vehicle. Contrary to popular belief a clogged air filter won't cause your engine to run rich because the initial fuel air mix is calculated off the MAF data a clogged air filter would just cause less air to pass the MAF and the ECM to add less fuel. This will also cause a rolling/uneven idle. A Basic Idle Tuning Strategy. The Edelbrock Performer RPM Q-Jet carburetor has conven-tional Idle Mixture Screws (IMS) that provide a leaner Air/Fuel (A/F) ratio when turned clockwise and richer A/F ratio when turned counterclockwise. Edit: Replacing the MAP sensor (which was suspected to be somewhat out of calibration on lower pressure readings after doing a vacuum gauge check) seems to have fixed the lean idle. Using AutoTap, I determined that it had to be my EGR Solenoid. Then turned up the fuel on the idle via the MAFT as far as it would go and the voltage moved around a bit for like 20 sec then dropped back to zero and stays at zero now. Cars with aggressive setups and big injectors may need a P gain of 0 and an I gain of 0. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). Warm idle shows a -6 to -8 % long term fuel trims. 7:1 and in reality it's neither truly lean nor rich. The long term fuel trim (FT) is a matrix of cells arranged by RPM and MAP. I estimate the lambda to be about 1. 7 units of air to one unit of gas. 3 positive on each bank and my long term stayed in the negative 3 range on both banks. Scan the LFT and Barometer (BARO) sensor readings. If you experienced the second result, you probably have too much Base Running Airflow added (Airflow Final Minimum table). 7 g/s of air at engine warm idle, 700 rpm. but still it's worth checking out. 4% Long term fuel trim 1 was -17. Idle Speed Error" Zero out that map! Then the timing won't change. but should not cause a high idle. If this condition exists, the LTFT is changed and acted upon during the next PCM timed cycle, which is every 10 minutes. The outlet pressure of the injector must remain constant. Engine Be certain the engine is Management WorksheetUse ONLY OBD II scan For Catalytic Converter Operation at operating temperature and in closed loop. If the numbers are high, it tells you the engine is running lean and the injectors need cleaning. This indicated a vacuum leak. but should not cause a high idle. Nevertheless the MAP system can cause small discrepancies in air-fuel ratio but the O2 sensor inputs will intervene in a short time and adjust the fuel trim as necessary. The ideal fuel trim values are around 0 percent. The ecu has modified the fueling tables. OIL PRESSUREOil pressure (at normal operating temp. (likewise if liquid fuel comes out of the hose). Idle Trim Rate Neg = At Idle, the fuel trim can be slowed to improve the stability of the AFR and engine speed. You might want to drop a pilot jet size. It eventually stopped. At approximately 13. I have no new codes but a slight hesitation when I get on it. There could actually be too much fuel going to Bank 1, but -35 percent fuel trim is still considered "in fuel control," so the engine should be running well. Connect voltmeter positive lead to DLC terminal #1 and Negative lead to terminal #12 (ground). Scan the LFT and Barometer (BARO) sensor readings. Once I start driving ,however, both the STFT and long term fuel trim approach normal limits (i. 3 300 Hp Warm engine rough Idle. The fuel trim behavior chart for an air metering issue looks very similar to a fuel volume issue (figure 3), but there are differences. During closed-loop fuel control, the fuel trim strategy learns the corrections needed to correct a "biased" rich or lean fuel system. The STFT pre-cat drops to about 1% at engine warmup. Engine Stalls, Misfire Code, & Cylinder Misfire The engine may be stalling because it isn't getting enough throttle opening. This is why I recommend testing fuel trims at a steady cruise when testing a MAF. Good fuel trim numbers are 0% or as close to 0% as possible. 9FF SC + NOS + PPV front struts + Bilstein rear shocks + 6L90E with single piece carbon fibre prop. Idle Trim Rate Neg = At Idle, the fuel trim can be slowed to improve the stability of the AFR and engine speed. With blue driver I could see the long fuel trim on the bank 1 way out of range (between 15 to 20) which I believe is compensation for a big lean condition. Note that both Banks 1 and 2 will exhibit negative corrections for 2-bank system. During Closed Loop, the ECM adds HO2S inputs to calculate the short and long term fuel trim (FT) adjustments. This long–term fuel trim is adjusted when there are persistent deviations in the short–term fuel trim values. If your trims are negative, lower the numbers. Extremes in either attitude can cause the boat to swamp. hydrocarbon (HC) emissions. The LTFT works to bring the STFT close to a 0% correction. Seems to sit roughly -4% which isn't massively out of whack (I would say). Conversely, if. So what next? To answer this question, consider what makes a diesel engine tick. I also noticed that fuel trim values at idle had too much difference with about -7% total trim on bank 1. This indicated a vacuum leak. Additive mixture adaptations: This adaptation is referred to as "short term fuel trim". Before driving, turn on the ignition and let vehicle idle for a couple of minutes to let the PCM reprogram its idle settings. A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. Positive fuel trim means the ECU thinks the motor is running lean and is adding fuel. Vehicle performed the same after a/f sensor install. Each cell of the long term FT is a register like the short term FT. Rough, erratic idle that drifts toward higher RPMs than expected based on the setting of the curb idle screw. If the TCM detects a faulty TPS signal, it provides continued operation of the transaxle by using the TPS value sent over the communications bus. It can be the switch, but that seems to be rare. Fuel Background The stoichiometric ratio for any internal combustion four stroke gas engine is 14. IAC- Hot start issue, high or hunting idle. If the vehicle stalls, re-start it, and let it idle for about 10 minutes. Turn your key to the run position and listen for the pump to work. Always stop the engine and DO NOT smoke or allow open flames or sparks in the area while servicing any part of the fuel system. What remains the same is that fuel trim numbers increase as RPM increases. The cable should be either twisted or shielded. The long term fuel trims (LTFT) are driven by. Engine should be at operating temperature. NEGATIVE FUEL TRIMS possible SOLUTION in BMW e46 Many things can cause negative fuel trims like bad fuel pressure regulator,leaking injector,MAF,bad oxygen s Skip navigation Sign in. The EGR valve receives vacuum at the proper time during a road test. At 2500rpm with no load, LTFT goes to +5%. Installed new air fuel ratio sensor and test drove. Note that STFT is negative and follows closed loop lambda operation. If idle or cruise trim is positive, then you need to increase the latency value. Engine Stalls (Check Engine Light May or May Not Be On). During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. This causes problems with carbureted engines vs not being an issue in an automobile engine with variable fuel injection, Further, there is no tetra ethyl lead in todays gas. Evap purge solenoid seems to pass a lot of air but there are times when it does not operate and the fuel trim remains high. anything -10 to +10 is acceptable tho but will cause either a power loss or fuel mileage loss. FUEL AND IDLE CONTROL VALVES FUEL CONTROL VALVE (FCV) An electrically actuated control valve used to trim off idle fuel mixtures by controlling the pressure on top of the regulators secondary diaphragm. 2014 Jetta SE 1. We honestly want to help. In general, if a short-term trim goes above 10%, this creates a long-term fuel trim that is semi-permanent (the exact way that this happens, as well as threshold percentages, varies by manufacturer). 2007 with about 170,000 miles. Couldn't tell you why, it would be nice if Honda just left everything the same. Lean mixtures also increase the risk of spark knock (detonation) when the engine is under load. Whatever is causing the high negative fuel trim needs to be figured out. Make sure your fuel pressure does not exceed 6. The NTS system functions in flight during temporary fuel interruptions, air gust loads on the propeller, normal descents with lean fuel scheduling, or high compressor bleed-air conditions at low-power settings. When certain conditions have been met to begin learning fuel control (ECT, closed loop, etc. Something interesting in the code is an idle correction factor during it’s airflow calc process. Fuel injector flow rates, atomization and distribution are affected and this can cause all sorts of drive-ability and performance problems. 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. ECT (engine coolant temperature) sensor Technician A says that the ECT and IAT sensors can be tested visually, as well as by using a digital multimeter or a scan tool. Most recently the fault code occurred after an air filter was incorrectly installed allowing unfiltered air to get into the airbox. The best way to approach this is to look at Long Term Fuel Trim data with the proper scanner, in at least 3 scenarios---idle speed, 3000 RPM unloaded and 3000 rpm with a load. - However, this causes some issues: o This causes the BOTTOM end of the throttle to have to be adjusted by altering the subtrim value. See the map called "Spark Offset vs. , it senses too much air, so too much fuel is injected for the actual amount of air, and the O2 sensor is used by the ECU to get the AFR back down to stoich. Since your off idle LTFTs are lower, the small vacuum leak does not have a very big effect at the larger throttle opening. When all the way down this provides you with a few degrees of negative trim. The main question I wanted answered was not whether or not I have an air leak. A bad fuel pressure regulator can lead to a build-up of excessive gasoline that can lead. Changes in o2 sensor voltages cause a direct change in fuel. The LTFT works to bring the STFT close to a 0% correction. A bad MAF sensor will tend to have positive fuel trims at load. To increase engine speed, the system adds fuel; to reduce engine speed, the system reduces fuel; a healthy diesel engine runs with an abundance of air and uses the heat of compression to produce combustion. It came back with rear o2 sensor, map sensor, cam. Whatever is causing the high negative fuel trim needs to be figured out. An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. I swapped the COP with number 6. I had a misfire on number 5 cylinder. A negative fuel trim value means the computer is subtracting fuel, while a positive value means the computer is adding fuel. Engine idle refers to the lowest rpm or speed at which the engine turns over when the driver is not depressing the gas pedal, according to 2CarPros. ( from research i should be at -22Psi ? ) My RPM at idle seems to be about 600~ should be 650 if I'm not mistaken, although I'm probably due for a throttle body cleaning. However, experience has shown that a very small leak in the inlet can cause uneven idle, without being enough to upset the fuel trims and without setting any DTCs. Another possible cause is the Idle_Decel table. If your trims are negative, lower the numbers. Remedy? Try adding a bottle of fuel injector cleaner. This change in fuel being added or taken away is called Fuel Trim. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. One or more of the PIDs are out of range when compared to "known good" values. Sensor working properly seeing too much oxygen and despite increased trim still running too lean based on massive vacuum leak (should have high idle) or insufficient fuel delivery based on injector clog dirty or bad harness expect code for one or more single cylinder miss or inadequate fuel pressure at rail expect worse stumble at high load. If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. For the long term fuel trim values, Durametric calls them (for my '07, DME 7. The DME adds the proper amount of fuel for 80cfm. Indicating a bad signal from the air/fuel ratio sensor, spec is 0% + or - 5%. Sudden decrease in fuel mileage. Very high long term fuel trims Does anyone have any ideas on how my Long term fuel trim's can be 28-30% on bank 1 and bank 2 but yet live monitoring of the AFR during tooling around town as well as WOT is well within spec. Some time ago Cummins issued a service bulletin to change the wiring from the old connector and lead that. Check engine light is off and vehicle out of limp mode. The same thing can happen if the hose that connects the valve to the throttle body, carburetor or intake manifold pulls loose, cracks or leaks. (Bank 1 sensor 1, Bank 2 sensor 1) Long term and short term are pretty much like they say. 7:1 and in reality it's neither truly lean nor rich. The LTFT works to bring the STFT close to a 0% correction. When the feedback from the HO2 sensors shows a deviation, the PCM adjusts the amount of fuel the injectors deliver, in an effort to hit the stoichiometric goal. Always evaluate fuel trims at idle and at 2500 RPM. A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. In this case, the idle was. When all the way down this provides you with a few degrees of negative trim. Idle air control valves and dirty throttle bodies can also cause idle problems like this. 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. A Basic Idle Tuning Strategy. The middle trim is for medium cruse rpm's (1500-2500ish) and the high fuel trim is for 2500+ rpm. While diagnosing an idle speed problem: Technician A says that higher-than-normal TP signals at idle will cause the IAC to close, which will decrease idle speed. xml file, to keep it as a backup, and download this file to try if you want. Fuel trim tables are based on engine rpm and engine load. After replacing the MAF and correctly torqueing the mount bolts I seem to have corrected the idle trim however now the fuel trim swings negative at low rpm. STFT's between two banks are almost identical and are almost always positive, meaning ECU is adjusting for a lean condition, which by the way should be normal since I have an aftermarket CAI that is obviously allowing much more air into the engine causing more fuel to. With the help of a diagnose tool, I've managed to read the Long/Short fuel trims and air/fuel. If the LTFTs are consistently in positive trim during idle and the engine is difficult to start while cold, then suspect that the fuel. Side note if you have a negative fuel trim you more than likely have an ignition related misfire. Took it off and put a piece of cardboard over the orifices and then my fuel trim came to life. LTFT is much more stable over time, and is a positive value. Short term fuel trims. L Droop/Idle Input Droop mode and Idle speed setting input. This can be a negative or a positive fuel trim. Good fuel trim numbers are 0% or as close to 0% as possible. 30 volts Fuel Trim Diagnostics Idle 2500 RPM Possible Causes HO2S AFR Testing 4. Mechanical Misfire Mechanical problems can also cause an engine to misfire. A mass airflow meter would usually set a fault code when you are driving, or at a higher RPM. Trying to find a junkyard part. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). Drive the vehicle to complete the relearning process. 0 psi, optimum pressure is 5. A negative fuel trim is considered anything at or below the minus 10 percent threshold. Negative LTFT's indicate the PCM is commanding less fuel due to what is perceived as a rich condition although the air-fuel ratio remains the same at 14. When it comes to the modern vehicle sitting in your garage today, you shouldn’t let your engine idle. 1) Possible causes. In general, if a short-term trim goes above 10%, this creates a long-term fuel trim that is semi-permanent (the exact way that this happens, as well as threshold percentages, varies by manufacturer). Pull the vacuum line and see if it is wet inside or if any fuel drips out of the regulator. Same with the fuel pump bleeding down, that may give you starting problems but won't cause your trim problem. Fuel injector flow rates, atomization and distribution are affected and this can cause all sorts of drive-ability and performance problems. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. Too fast of an idle. 65 seconds, the short-term fuel trim (STFT, green trace) begins to go negative and quickly goes to. Prime the fuel rail by turning the key to the ON position for 2-secs. Assure there are no vacuum leaks then go. Top 10 Most Common Problems with 1993-2000 850, C70, S70 and V70 Models Thursday, August 27, 2009 - ipd staff We’ve put together a list of some of the most common problems you might run into if you own or are considering one of these models. A small vacuum leak has a big effect on the LTFTs when at idle. Press and hold UP and DOWN arrows simultaneously for 3 seconds to UNLOCK or LOCK the display. Also getting p0174 have replaced fuel pump and filter which wasn't bad and smoked engine and no negative results. 0 in the short trim. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over- estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). The DME adds the proper amount of fuel for 80cfm. What I want to know is how to use the Durametric to understand and monitor the performance of the car. but should not cause a high idle. The powertrain control module (PCM) controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Engine speed should increase 50 RPM, and idle speed feedback should remain at 128 17. The long term fuel trim (FT) is a matrix of cells arranged by RPM and MAP. In your C:\Program Files\EvoScan\EvoScan v2. When both banks are showing lean operation at idle speed but the values decrease to single digit readings in an off-of-idle running condition, the suggestive cause is a vacuum leak concern. 5\DataSettings\ folder you can rename your Data. s suggestion is correct. Idle air control valves and dirty throttle bodies can also cause idle problems like this. From the tank, there is a feed line that runs through the fuel filter and up to the fuel rails, which supplies the injectors with fuel. Idle Air Trim Idle Air Trim is designed to adjust the Idle Air Control (IAC) calibration to correct for wear and aging of components. A rich biased O2 sensor may cause inappropriately negative fuel trim on one bank, resulting in a lean misfire. Issues like leaking fuel injectors, a defective fuel pressure regulator and defective MAF sensors will be addressed. What are short and long term fuel trims at idle and 2500 rpm on each bank? Total fuel trim values are short plus long term as long term fuel trims goal is to keep short term fuel trim as close to zero as possible. Each cell of the long term FT is a register like the short term FT. You may encounter a customer concern of oil consumption, oil leaks, blue smoke from the exhaust, MIL or fuel trim codes. A weak fuel pump can show up as fuel trims off in either side. STFTs are used at idle and part throttle. Plugging is usually caused by unburned fuel entering the exhaust system. Once I start driving ,however, both the STFT and long term fuel trim approach normal limits (i. 4% Long term fuel trim 1 was -17. A weak fuel pump can show up as fuel trims off in either side. Power balance test was showing sporadic reduced contribution from different cylinders. Some common causes are: MAF malfunction, incorrect signal information sent to the ECM Low fuel pressure, faulty fuel pump Unmetered air leak, such as torn intake boot, etc Pressure regulator malfunction Excessively negative multiplicative adaptation values indicate rich condition. My log shows -10% fuel on bank 2. How long you should disconnect the battery is a matter of debate. 000 km, spark plugs, air filter, oil were changed recently, no cell. Don't know much about these parameters, but I read just the other day that when a MAF starts to go or gets dirty, it can cause a rich condition at idle and lean condition at higher rpms. Always stop the engine and DO NOT smoke or allow open flames or sparks in the area while servicing any part of the fuel system. The PCV may cause a rough idle, hard starting and lean misfire (which increases emissions and wastes fuel). Couldn't tell you why, it would be nice if Honda just left everything the same. So, your car fuel economy will affect significantly. Fuel trims ate running way negative, sometimes up to -30. Test by attaching a fuel pressure gauge. Take a close look under the Jeep to ensure there are no fuel leaks. For all this reason, repairing a cracked fuel injector is an auto repair you should learn to do on your own. During periods of idle or trolling, trim the engine up at least half-way so the "heavy ends" of fuel and oil will reaach the recirculation system. A vacuum leak will cause the engine to run lean. It requires a larger leak to drive the Fuel Trims high enough to set a DTC. The primary fuel enrichment is a multiplier (determined primarily by the open loop fuel maps) applied to the base injector duration to determine the level of primary enrichment. Using the tester, switch the ecm from normal mode to check mode (see page es-38). Negative numbers represent the PCM removing fuel from the system. The idle air flow is controlled by a conventional screw that opens the primary throttles. During warmup it was acting perfect. Throttle Potentiometer or Idle Speed Stepper Motor: Faulty Potentiometer or wiring, or faulty idle speed motor or wiring: 1233: Wheel-speed sensor FL: Speed sensor cable, wiring connection, speed sensor, excessive or insufficient gap between sensor and pulse wheel, sensor or wheel dirty or damaged: 1241: Wheel-speed sensor FR. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. This monitor uses the fuel trim correction levels for detection. If the fuel gauge is fluctuating it is likely because there is excessive vacuum in the tank. 6 then by 1300 rpm all is perfect This truck runs perfect, no warning lights, just playing with my fuel trim data What would cause bank one to run rich at idle ONLY ON LTFT DATA. Always stop the engine and DO NOT smoke or allow open flames or sparks in the area while servicing any part of the fuel system. Trying to find a junkyard part. Vacuum leaks play a big difference at idle but very little at higher rpms. Motorcraft is a global leader in aftermarket products to repair your vehicle. It was recently mapped and Duncan noticed it was running rich, but was unable to lean it out without causing running issues. The system (engine control unit) does not "foresee" any fuel corrections. However my truck seems to have a little bit of a rough idle and rpms fluctate with that rough idle. If the control module. Now, if they checked the O2 and did not mount that right or well, I suppose a leak there would throw things off. The same thing can happen if the hose that connects the valve to the throttle body, carburetor or intake manifold pulls loose, cracks or leaks. 5\DataSettings\ folder you can rename your Data. In the "Old" days, that was a stuck choke. For fuel mixture check (O2 feedback) operation, refer to Diagnostic System Operation Manual”. Do not touch the accelerator, or move the vehicle during this time. My 2wd 2000 Honda CRV with automatic is showing rather large negative adjustments to the short term fuel trim (STFT) at idle. The DME adds the proper amount of fuel for 80cfm. The pre-catalyst exhaust gas oxygen sensor is the primary component used for calculating the fuel trim once the system enters closed loop control. Lean mixtures also increase the risk of spark knock (detonation) when the engine is under load. P0171 BUICK Meaning The Engine Control Module controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Also the the long term fuel trim (LTFT) will also decrease at idle to below -5%. A vacuum leak will cause the engine to run lean. 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. Match the colored flags on the lines to the colored dots on the. Side note if you have a negative fuel trim you more than likely have an ignition related misfire. Fuel trim is an adaptive control strategy used by the PCM for adjusting the pre-programmed injector pulse width. Having bad fuel injectors can cause bad mileage. I had the dealer that I use run a full computer scan on it. • The amperage will be negative to try to maintain 3. High values of AFC (especially at idle) in closed loop operation indicate poor mapping. The approximate airflow ranges for the three trims are: Low: 0-125 Hz Mid. The short term fuel trim value will be between 128-147 indicating a lean condition. I added some injector cleaner/ fuel stabilizer stuff (we dont have seafoam here and this was the closest thing I could find) into the fuel tank - bear in mind I am pretty sure this was crap fuel anyway. Side note if you have a negative fuel trim you more than likely have an ignition related misfire. Read the misfire counts of each cylinder (cyl #1 to #4) with the engine in an idling condition. 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. anything -10 to +10 is acceptable tho but will cause either a power loss or fuel mileage loss. • This is how the system has a tendency to runtendency to run • An acceptable range is +/- 10%. Some time ago Cummins issued a service bulletin to change the wiring from the old connector and lead that. A defective O2 sensor will likely cause your air-fuel mixture to be too rich and directly affect your fuel economy. A negative fuel trim value means the engine computer is subtracting fuel. This value adjusts how quickly fuel is increased (towards richer). The best way to tell if it's a vacuum leak is to look at fuel trims at different RPMs. This is typical of a dirty MAF sensor. Started to look at O2 sensor bank 1 sensor 1, which seems to be a DIY'ers nightmare. While diagnosing an idle speed problem: Technician A says that higher-than-normal TP signals at idle will cause the IAC to close, which will decrease idle speed. Then turned up the fuel on the idle via the MAFT as far as it would go and the voltage moved around a bit for like 20 sec then dropped back to zero and stays at zero now. This is useful to determine when the ECU is running in open/closed loop mode i. As a result STFT will always fluctuate, from positive to negative, but LTFT will tend to converge to O2 sensor inputs. Turn the tester on. (WOT), the computer is in open loop and the O2 readings are not part of the fuel ratio calculations. 0 and flipped me out,,nothing was changing. Note that STFT is negative and follows closed loop lambda operation. The fuel trim looks ok. Seminar Objectives or extended idle conditionsor extended idle conditions. LTFT is much more stable over time, and is a positive value. Therefore, negative fuel trim makes it much more likely that fuel trim is causing the misfire than reacting to it. LTFT near zero). Adaptive Fuel Viewer Service Tips ─ 2013 and Newer Vehicles Fuel control system is detecting a lean condition at idle that decreases through all load ranges. Note that STFT is negative and follows closed loop lambda operation. You can see signs of high exhaust back pressure on a scan tool; calculated load will be low at wide-open throttle (WOT) and fuel trims will trend negative as engine speed increases. STFT is used for immediate adjustments based on the parameters, whereas the LTFT is a slower adjustment. 30 volts Fuel Trim Diagnostics Idle 2500 RPM Possible Causes + 5% and Up 0% Vacuum Leaks 0% + 5% and Up Low Fuel Volume HO2S AFR Testing 4. If the STFT shows an increasing trend, the LTFT will increase and allow the STFT to normalize and. 2L MPI gasoline engines. Keep in mind the fuel trims might be positive or negative, depending on the fuel vapor present in the charcoal canister. I would strongly suggest doing some routine maintenance to your ski. Normally, a vacuum leak would set a fuel trim fault code at idle or very low engine RPMs. What remains the same is that fuel trim numbers increase as RPM increases. What it has done, is at some point both banks' primary lambda sensors have reported a rich condition for an extended period of time. On hand held find "IAC STEP" adjust idle screws (both sets) 1/8" to 1/4" turn equally until IAC STEP is 5-10. Vvt gear, timing chain , vvt solenoid, and chain tensioner were changed. The prop can overspeed and cause propeller or gearbox damage. The best way to approach this is to look at Long Term Fuel Trim data with the proper scanner, in at least 3 scenarios---idle speed, 3000 RPM unloaded and 3000 rpm with a load. Set idle speed to desired RPM. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. Common culprit is the coolant temp sensor (ECT). Note though that since sudden changes in the engine speed can cause short-term fuel trim values to fluctuate wildly, all fuel trim values should be taken at a minimum of at least three steady engine speeds, these being at idle, at about 2500 RPM, and at about 3500 RPM. You need a more advanced OBDII code reader (like AutoEnginuity) to read the fuel trim values. Fuel filter has about 14,000 miles on it. The MAF sensor overestimates airflow at idle, which causes the negative fuel trim values. STFT's between two banks are almost identical and are almost always positive, meaning ECU is adjusting for a lean condition, which by the way should be normal since I have an aftermarket CAI that is obviously allowing much more air into the engine causing more fuel to. Something interesting in the code is an idle correction factor during it’s airflow calc process. 7 g/s of air at engine warm idle, 700 rpm. An OBD II truck with MAF shows lambda at. The car thinks it is getting too much fuel. I plotted long term fuel trim, at idle LTFT is down about -18%. So, your car fuel economy will affect significantly. P2189 System Too Lean at Idle (Bank 2) P2193 System Too Lean at Higher Load (Bank 2) All related codes are similar but depend on general operating conditions at the time the fault was noted, which may help in determining the cause. I don't know about the fuel cuts, but for the irregular idle it could be something jamming the throttle cable and holding the butterfly valve open, I had something similar when I first completed my swap, with the corolla 2zz angled throttle body causing the throttle cable to impinge on the firewall ledge and jam, it confuses the heck out of the ecu. 0 psi, optimum pressure is 5.
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