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Fuel Trim


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Trim, Duration, O2
Fuel ___ is a command from the PCM to alter injection ___ as calculated from the ___ sensor readings
Rich, Subtracting
Neg FT means there is a ___ condition so computer is ___ fuel
Lean, Adding
Pos FT means there is a ___ condition so computer is ___ fuel
Limit, DTC
If a trim goes to its ___ a ___ is set
Short Term, Long Term, Additive, Multiplicative
Types of fuel trim ___ ___ and ___ ___ or ___ & ___
25, Injection
LTFT of +/- ___% means the computer can't adjust the ___ duration enough to compensate for the problem
Factory, 0, 10
LTFT will adjust from the ___ preset to keep STFT near ___% with +/- ___ % movement allowed.
10, LTFT, STFT
A Pos or Neg value over ___% of the STFT reading is transferred to the ___ to allow the ___ to reset to 0%
LTFT, Adjust
On vehicle start the computer uses the ___ to ___ the injectors ms opening time
Load RPM, LTFT
Different ___ / ___ combinations may have different learned ___ numbers
10
Percentage range considered to be within normal specifications +/- ___%
Closed, Open
STFT is only used in ___ loop, although LTFT is used in both ___ and Closed Loop
Add, Subtract, O2, Trim
Computer will ___ or ___ fuel until the ___ sensor averages 0.450mV again or until the ___ reaches its limit
5
If LTFT is 30% and STFT is -25% after a part change then problem is fixed as total FT is only ___%
Lean, 20
If LTFT is 30% and STFT is -10% after a part change then you still have a ___ condition as FT is still high at ___%
Additive
BMW : Idle FT adaption used during idle and low load mid range engine speeds
Multiplicative
BMW : Part Load FT adaption used during normal to higher load or at higher engine speeds
Add, Vacuum
If additive adaption is 0.5ms then ECU is trying to ___ fuel and is likely to be a ___ leak
Add, MAF
If multiplicative adaption is +10% then ECU is trying to ___ fuel and most commonly a ___ problem
Add
VW : ___ means additive trim used to correct an imbalance at idle.
Mult
VW : ___ means multiplicative trim used to correct an imbalance at all engine speeds.
Less Significant
A vacuum leak becomes ___ ___ as RPM increases, so expect less correction in fuel trim at higher RPM
Higher, Mult
A clogged injector is more severe at ___ rpm, if so we would expect more correction the ___ readings
80, 120
Test MAF : Peak MAF readings should be ___% of vehicle horsepower, so 150hp vehicle has ___ g/s
32, Additive, Multiplicative
VW : Group ___ shows Trim, 1st field is ___, 2nd field is ___
14.7, 1, Rich, Lean
A/F ratio is ___: 1 = Lambda value of ___, if Lambda < 1.0 then mix is ___, > 1.0 then mix is ___
LTFT, Adaptive Fuel Strategy
Resetting the DTC's resets the ___ back to the factory preset of 0% clearing the learned ___ ___ ___
LTFT, Learned
___ is an adaptive fuel strategy that's ___ and is not reset with Key Off but STFT is reset on Key Off
O2, 450, 200, 800, STFT
Goal of the ECM is for the ___ sensor voltage to average ___mV (moving between ___ - ___ mV) and the ___ at “0” +/- 10%.