Long Term Fuel Trim

[Andy K]

Hi

On a 2001 car, are there different fuel trims stored for different rev ranges ?

I appear to have a condition where the LTFT is ok at idle however, between 1300-1600 its -20.

Thanks
Andy

[Ayman Kamar]

may be dirty maf
or
weak fuel pump
dirty fuel filter

[Apex]

Yes, the computer will store fuel trims over a range of RPMs, I would imagine this is stored in a similar table to how the normal fuel calculations are done (watch some videos on how tuning is done, for example).

However, it is important to look at both STFTs and LTFTs at the same time no matter what.

[Andy K]

Yeah I’m looking at the ST when reved @1600 and its bad. -19 I think

At idle and higher RPMs its a more acceptable value. (single figures)

And yes the LT is bad too.

Note to self, I had to change the fuel pumps a few days ago.

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