What is a normal long term fuel trim reading?
Values normally range from negative 10 percent to positive 10 percent, though the readings may jump as much as 25 percent or more in either direction. Long Term Fuel Trim (LTFT) is a longer term average of what the engine computer has been doing to balance the fuel mixture over a predetermined interval of time.
How do I reset my long term fuel trim HP tuner?
while you’re logging, open the vcm controls, hit reset fuel trims. your LTFT’s will go to zero as soon as you do it.
Why is my long-term fuel trim negative at idle?
During idle when the throttle plate is closed, the vacuum in the intake manifold is high and very little air flow is entering the engine, so even a small amount of un-metered air will have an effect on fuel trim. This causes the fuel trim numbers to become negative during a boost situation.
Why is my long-term fuel trim negative?
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.
What causes negative long-term fuel trim at idle?
What should bank 1 fuel trim be at idle?
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 as a vacuum leak.
What happens if the fuel trim system is too lean?
Indirectly, the ECM can judge air-fuel ratio and adjust for emissions. If the ECM detects that the oxygen sensor is stuck lean, that is, it is not switching from lean to rich to lean, it records this as a fault, stores a DTC, and illuminates the MIL (malfunction indicator lamp).
What is the long term fuel trim strategy?
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. Once the engine is up to operating temperature, the PCM/ECM employ a short term fuel trim (STFT) strategy.
What should the LTFT be for bank 1?
If the LTFT for bank 1 is 20% and the LTFT for bank 2 is 3%, the source of the problem is associated with bank 1 cylinders only. The diagnosis should focus on factors related to bank 1. If an engine vacuum leak is suspected, inspect the intake manifold and vacuum hoses for leaks.
https://www.youtube.com/watch?v=RrkPS9s7UBU