What should STFT be at idle?
Short Term Fuel Trim (STFT) is what the engine computer is doing to the fuel mixture right now. 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.
What does STFT B2 mean?
STFT B2 is Short Term Fuel Trim engine cylinder Bank 2. LTFT B1 is Long Term Fuel Trim engine cylinder Bank 1. LTFT B2 is Long Term Fuel Trim engine cylinder Bank 2.
What does STFT B1 S2 mean?
Those are the catalyst monitors see where it says B1 S2 that means bank 1 sensor 2 you want to see a high % there as it shows no unburned fuel air/gas coming out. STFT is mainly relevant for B1 S1 and B2 S1 and that will vary depending on how well the engine is running.
What is normal STFT and Ltft?
Short-term fuel trim (STFT) and long-term fuel trim (LTFT) are expressed as a percentage, and the ideal range should be within 65%. 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.
What causes high STFT?
A significant increase in STFT and LTFT can be caused by: Unmeasured air is entering the engine due to a vacuum leak (higher fuel trim at idle, but less at higher RPMs) Incorrectly reporting sensors (dirty MAF reporting less airflow) Dirty or blocked fuel injectors.
What does a negative STFT mean?
LTFT refers to changes in STFT but averaged over a longer period of time. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. A normal long-term fuel trim reading will appear to stay the same, giving a long-term average of fuel added.
What is a STFT B1?
STFT B1 is Short Term Fuel Trim engine cylinder Bank 1. STFT B2 is Short Term Fuel Trim engine cylinder Bank 2. LTFT B1 is Long Term Fuel Trim engine cylinder Bank 1.
What causes positive STFT?
One thing that restricts airflow into the cylinders is a damaged catalytic converter that causes high exhaust back pressure. At idle this can drive fuel trims in opposite directions, producing a positive STFT and negative LTFT.
What is a normal reading for an oxygen sensor?
between approximately 0.1 and 1.0 volts
A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1 V to 1.0 V (referred to as the lean to rich response time) should be about 300 milliseconds.
Why is STFT high?
What does Ltft do when STFT gets too far away from it?
STFT is used for immediate adjustments based on the parameters, whereas the LTFT is a slower adjustment. The LFTF value is stored in memory and “learns” from the STFT. If the STFT shows an increasing trend, the LTFT will increase and allow the STFT to normalize and vice versa.