The percentage reading represents the difference either above or below the anticipated amount. A fuel trim of +25% for example means the ECM is adding a LOT of fuel. Additionally the vehicle speed displayed 0 at test drive. , a vehicle is being diagnosed with a low fuel pressure problem. If a fuel trim is positive, it means the injectors are adding more fuel to reach a balanced combustion event. Fuel trim is the adjustment the engine computer makes to the fuel mixture to maintain a balanced air/fuel ratio. An oxygen sensor monitors the flow and generates a signal that is proportional to the oxygen levels in the gases. Depending on how long things were out of whack, the O2 sensors could be the problem now. This will get you to your desired trim much quicker than trims which have been in place for a while. The passenger bank LTFT reads steady at . Speed of the vehicle Technician. Changes in o2 sensor voltages cause a direct change in fuel. Was -20 to -25 (idle) LTFT 0 to -2. 4 4x4 TRD ( <3), '06 Taco Prerunner 4. The long term fuel trims (LTFT) are driven by. 1 (855) 347-2779 · hi@yourmechanic. A/F is expressed as either a ratio (14. MAF engines show big changes in fuel trims at idle speed with an kind of vacuum leak "pirate air" the trims add a lot of fuel at idle to compensate, but much less extra fuel at 2,000 rpm. The car will always shoot for ~14. The regulator routes excess fuel back to the gas tank to maintain fuel. Not entirely sure how you can say it's non sense. When I rev the engine to 2500 all LT and ST trims go to normal. During•171, 172, 173 (HO2S11 lack of switching, Bank Always verify the STFT (short-term fuel trim) and the LTFT (long-term fuel trim) while reading live data from the OBDII scan tool. At -25 or higher the PCM is maxed at how much it can correct the mixture and you will get a code po172,po175 rich bank 1 and rich bank 2. 5 on both short and long term fuel trim before (at WOT). I haven't seen any trouble codes yet, but gas mileage hasn't been very good. Plug the cable into the car and to the laptop and turn the ignition on. ² When Monitored: With the engine running in closed loop mode, the ambient/battery temperature above (-7°C) 20°F, altitude. Info: 2012 1. The intent here is simply to describe the help I am seeking in a more concise manner. The Long term Fuel Trim is back to 25% at idle, even with the replacement MAF. Here are the correct readings for a Boxster MAF at idle AND at 3000 RPM. Postby Ludeaem » Sun Nov 07, 2021 4:35 pm. 3. A P0171 lean code for bank 1 is the cylinder bank on the RIGHT (passenger) side of the engine on Ford vehicles with a V6 or V8 engine and rear-wheel drive. No codes. The Long Term Fuel Trim reading will appear more stable. bluetooth stereo. Values are not that much off so the check engine lights is not on and no DTC thrown. Updated: July 10, 2021. If the fuel system is open loop, 0% correction should be reported. Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST. Have a 97 Escort 2. Long-term fuel trim averages several of the short-term readings to affect the fuel base mapping. Fuel trim is a calculation based on the O2 sensor readings from the sensors at position 1. A -20 percent short. 2 amps. Have a 97 Escort 2. Fuel trim is what the ECM implements to. And when the engine is running, the plunging piston motion creates a vacuum. 7:1 as possible. At speed and load, the fuel trim should be near normal as the EGR opening should be close to normal for these conditions. When I looked at the freeze frame data for p1443 the fuel trim showed different than -100. of air to 1 lb. 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. Fuel trim can also be expressed as either a positive (+) or negative (-) percentage. The long term fuel trims job is to keep the short term fuel. Fuel trim can also be expressed as either a positive (+) or negative (-) percentage. So it goes with using fuel trim data. Sent the first scanner back & received a another scanner today. But I'm not sure if these are long or short term fuel trim numbers. Now when the STFT is steady at 27%, the LTFT will increase to 27% to adjust the fuel delivery for a longer period. Idling trim data is telling me fuel delivery. This is known as "Stoichiometric", a. I currently run 10% ethanol gasoline in my Wrangler, RX350, and Land Cruiser. Connect a fuel pressure gauge to the fuel rail and make sure that the fuel pressure is correct. The MAF sensor simply measures the mass (amount) of air coming into the engine so that the PCM can add the correct amount of fuel. Short term is only indicative once the o2 sensors are at the proper temperature, so wait until you see readings from the o2 sensors before recording stft. P0171 Causes (Lean Bank 1) Faulty or dirty mass airflow sensor. Long-term fuel trim averages several of the short-term readings to affect the fuel base mapping. For example, if. 15psi delta (which is the pressure at which Ford Racing specifies the flow rate), the injectors will be correctly sized regardless of which fuel system you actually have, and also to show you that fuel pressure on ERFS vehicles can change based on a number of conditions. Code P0171 is caused by the fuel system running too lean (Bank 1). 0%. REAR FUEL TRIM: Since rear fuel trim (RFT) operating strategies vary widely among manufacturers, you’ll have to learn as you go. Nothing. Operate the vehicle at idle in park and record the fuel trim numbers. Be scared of anything above 10% or below -10%. 6 %. The effects of a stuck-open EGR are problematical because, on the one hand, chemically inert exhaust gas dilutes the air and fuel in the. The optimal reading for the STFT and LTFT is between 5% and 10%. 0L engine. Most common is 32. Note the idle readings, taken at 875 seconds (the green cursor): Calculated Load 40% MAP 11. Faulty evaporative emissions system - bleeding fuel vapors into engine (not commanded by computer) 5. The STFT was at +22% and the LTFT at +20%, and these trims were occurring at idle on a warmed-up engine. 14% is a bit high. A negative fuel trim reading tells you the computer is trying to cut back on fuel. I have just installed 2 new O2 sensors and the Fuel Trim % for the B1S2 sensor is still pegged at 99. Issue was due to vacuum leak from broken CCV return hose (post #66) Details: Code. Ideally, both values should be at, or close to 0%, when the engine is running at a steady speed, such as when it is idling. Much later, when I got back home, the idle timing was -24 degrees, but the driving timing was still usually -33. For example, a car with a 0-60 mph time of 4. LTFT B1 is Long Term Fuel Trim engine cylinder Bank 1. #6 · Dec 15, 2016. Fuel Trim can be anything from a bad o2 sensor to a bad injector. Video: ProMAXX Ford 6. In this case, the fuel trim numbers are a recently cleared PCM’s response to a good O2 sensor. If the sensor spies excess O2 in the exhaust, the PCM will increase the commanded injector on-time to compensate. 1 above shows the fuel trim data collected on a vehicle with the. The car will always shoot for ~14. Many drivers simply don’t push their vehicles hard enough to heat the catalytic converter to its most-efficient temperature—between 800 °F (426 °C) and 1,832 °F (1,000 °C)—leading to premature. LEAN DTCS: In general, a + 25% or greater fuel trim correction will store P0171/P0174 DTCs. 2003 F150 SCREW 5. In a properly functioning system, the ECU will react and immediately make changes as the exhaust gases change. You also want the total trim values (short and long added together) under 10%. Some of the symptoms include: An illuminated check engine light. Elevate engine RPM to around 2000 to 25o0 RPM in park and record the fuel trim numbers. As the throttle is moved, and the engine load changes, the long-term fuel trim will jump from zero to a -24 percent. The whole time, the second fuel trim values (FT #1x2 and FT #2x2) have stayed very high almost all the time. As with LTFT, the number should usually be plus or minus five. 22%. Read FAQ. Re: Y33 - Short and Long term fuel trim value questions. Well a long term fuel trim in the negitives means that the PCM is subtracting from the base fuel trim. 7:1 in closed loop, but once the car is WOT, it can no longer correct an improper A/F ratio. The car has 4 new ATK o2 sensors installed. 1-. The fuel trim Parameter Identifiers (PIDs) on the scan tool are telling you how the ECM is adjusting the fuel injector’s “on time” (pulse width) in order to add the correct. 25%, intake manifold. this procedure is ½ fuel tank level. It has a '98 program in it also. OBD-II Trouble Code Chart. Fuel trim can also be expressed as either a positive (+) or negative (-) percentage. 9 reading is the same as -10%, and a 1. 9V on the MAP sensor with the engine operating above 2k rpm's. Here are a couple of others: A MAF sensor diagnostic trouble code (DTC) stored in your vehicle computer's memory. Vacuum leaks – PCV hoses, vacuum hoses, intake manifold gasket. Vac leaks trim leanest at idle and trend towards 0 trim under load. If the numbers are low at idle but climb on a part throttle cruise, the fuel pressure might be low or the mass air flow sensor could be reading low. They have a 10% window that will only affect the Long Term Fuel Trim (LTFT) if the fueling correction is beyond the 10% window for 10 seconds. LTFTs and STFTs are both 0% at idle. If greater than 10, it indicates a fuel mixture problem. tech b says percentage is used. But, because the O2 monitors are incomplete, the PCM does not yet trust them enough to have reached a correct fuel trim value. Codes 170 and 173 indicate an issue with the fuel trim for which the ECM can no longer compensate. The value is constantly around 80-90% or higher. LTFT refers to changes in STFT but averaged over a longer period of time. However, because of operating losses in the induction system due to intake runner and cylinder. 8 g/s. Avoid suddenFuel trim can also be expressed as either a positive (+) or negative (-) percentage. Reason 3: O2 Sensor is Faulty. Alright, reset ECU and have only driven about 10-15 miles but readings are better. 00 in. Monitor and record the fuel trim values in the four common operating ranges—idle speed, light load (20 to 30 mph), moderate load (40 to 50 mph) and heavy load (60 to 70 mph). A useful diagnostic tool is to determine if the fuel trim problem exists in more than one engine operating range. The P0300 pulls on moderate (1500-2000) RPMs. A week ago bought one of those obd2 code readers for the cell phone and here is the info from when the code appeared, that is P0300and P0420, Calculated engine load 13. Fuel injection jetting was adjusted until an optimum spark plug reading was achieved. Modular/Triton V8 Engines: 4. The percentage reading represents the difference either above or below the anticipated amount. Fuel trim bank 2 sensor 1 = FT 2x1. Tech B says that when the air-fuel ratio is at 14. The STFT and LTFT numbers represent the amount of pulse width change, typically as a percentage. 45 volts. :) Have seen it many times. 04 % They never. Tech a. So on your scan tool, you’ll see the short-term fuel trim readings switching back and forth between. 7 to 1 (14. That is where the long term fuel trim kicks in. Problem description: Starts and idles fine, but stumbles for about 5-10 seconds after I give it gas. A normal long-term fuel trim reading will appear to stay the same, giving. Check the Fuel Trim PIDs, if they close are to zero, less than 10, then the system is doing little to correct fuel mixture. 19. ts the engine’s performance. So a short term fuel trim reading of +20 percent indicates 20 percent more fuel had to be added to achieve the proper air-fuel mixture. In this case, STFT at idle was approximately 223% and LTFT was 24%, for a total fuel trim calculation of 227%. A Ford P0171 is a LEAN code for cylinder bank 1, and P0174 is a LEAN code for cylinder bank 2. Evinrude e-tec series 250, 300 hp 90 v6 (3. Post Catalyst Fuel Trim System Too Rich Bank 1. 5 to 1. MAP engines are more immune to the effects of vacuum leaks, with a MAP engine high or erratic idle. Im leaning towards maf. ” Then I was introduced to fuel trim data. 34%, long term fuel trim B1 +16. I've gathered the fuel trim readings from the car a couple more times after 30 mile drives. You will find a leak or a faulty one-way valve that is causing the P0171 code in most cases. temperature/pressure, ECT, knock sensors, engine load, throttle position, and even battery voltage can effect fuel trim. When I looked at the freeze frame data for p1443 the fuel trim showed different than -100. 7L I have read the article on this topic. The intake manifold vacuum reduces the original barometric pressure by around 9. Fuel trim is a key diagnostic parameter and tells you what the com-puter is doing to control fuel delivery and how the adap-tive strategy is operating. 7 gallons/minute and fuel pump current of 6. in your case at 3500 RPM 1 X 14. (856) 785 9455. 50. The next step is to check for vacuum leaks. LTFT refers to changes in STFT but averaged over a longer period of time. Look at the bank with the more negative correction for the cause. A short term fuel trim (integrator) reading of 118-138 is considered normal. Short Term Fuel Trim -Bank 1 -1. GET A QUOTE. The IAC counts are an important clue. 1 and at 2500 rpms B1 is 0 and B2 is still 3. The most likely culprit here is a leaking EGR. Compare all 1997 Ford Escort features and specs side-by-side in one place. Today, my LTFT started trending negative again and I noticed my MAF grams per second reading was inconsistent and unsually high (around. Runs pretty smooth at 2500. So a short term fuel trim reading of +20 percent indicates 20 percent more fuel had to be added to achieve the proper air-fuel mixture. The 3 codes I got in May were the p0170 (MAF) P0130 P0133 (02 sensors). Autozone has a GP/Sorenson FPR PN 800-302 listed for the 2000 PAU and 2005 PAU. Codes 172 and 175 indicate a rich condition in either bank 1 or bank 2. 2 posts • Page 1 of 1. If I swap for a new sensor, the short term trim values go up to 30% even as high as 40% and the long term values typically drop to 0% and hold so steady that it seems it isn't trusting the readings. The Long Term Fuel Trim is made up of accumulated data from Short Term Fuel Trim readings and stored as historical data for the ECM to quickly pull from.