High STFT1

[MustangPP1]

I remember it was supposed to be 0%, but mine is at 20%, what is happening?

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[Nuked]

Need more details. Is it plus or minus 20%, WOT, all the time, part throttle etc

 

[MustangPP1]

Need more details. Is it plus or minus 20%, WOT, all the time, part throttle etc

Plus 20%, i saw it at idle, I’ll check what percent it is while driving, but idle it’s 20%

 

[Lime1GT]

Read this for some insight. https://www.aa1car.com/library/what_is_fuel_trim.htm

 

[Nuked]

Check for any vacuum leaks. What all is done to the car?

 

[MustangPP1]

Check for any vacuum leaks. What all is done to the car?

Long tubes, h pipe, cold air, tuned, axleback

 

[MustangPP1]

Need more details. Is it plus or minus 20%, WOT, all the time, part throttle etc

Today it went to plus 6-10% at idle, while driving/cruising city its around minus 2 to plus 4. Saw it stay at 0% too

 

[ManBearPig]

Short trims move a lot. By definition they are constantly adjusting. Under steady throttle it should be near zero if the long term trims have adapted properly.

The short trims will be pretty far off at times though. When returning to idle, at strange throttle transitions, until the car is warm, etc.

 

[BigBlue]

Pull a datalog and look at your lambse and AFRs, then sum your LTFT1 and STFT1 adjustments to see what the car is doing to achieve the AFRs you are at. If the LTFT's are > +10% (11% or higher) or <-10% (aka -11% or lower), your tuner should be able to adjust the fueling so the car doesnt have to compensate so much. Once the fueling is primarily dialed in your LTFTs will settle closer to 0 (or at least much less than 10% +/-) and your STFT will adjust as needed to keep you at the tune's desired air/fuels. If LTFT is constantly changing/not settling and STFT is going nuts, somethings up with one or more sensors as the car isnt "settling" in and/or the tune is way off.

 

[ahl395]

As said, STFT varies constantly. Take a look at LTFT for a bigger picture of what's going on.

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