How to disable fuel trims to adjust MAF

[sdhager]

I am working on a 98 Firebird LS1 auto trans. I have the VE table dialed in, and am attempting to dial in the MAF. I am also logging STFT and LTFT, just because. I have disabled B3801 (LTFT correction) and B1408 (STFT idle enable). Problem is that during my logging, the fuel trims are varying by about 6% +/-. What did I miss?

I also changed B3802 (Min ECT to enable LTFT) to 140'C.

[WeathermanShawn]

Make sure that prior to your next run you re-set the fuel trims to zero.

If you do not do this the learned values from previous runs will carry over, regardless of the fact that you just disabled those parameters.

Otherwise, sounds like you are doing it correctly. If that does not work, post a tune and log. But, that technique always works on my operating system.

[sdhager]

Make sure that prior to your next run you re-set the fuel trims to zero.

If you do not do this the learned values from previous runs will carry over, regardless of the fact that you just disabled those parameters.

Otherwise, sounds like you are doing it correctly. If that does not work, post a tune and log. But, that technique always works on my operating system.

Good luck.

..WeathermanShawn..

I thought the simple matter of reflashing the computer would erase (reset) the fuel trims.

Is this wrong?

[joecar]

Don't you have to disable B4205 (CL temp enable) also...?

[WeathermanShawn]

Good call Joecar.

To not have LTFT's I have always disabled B4205 (set to it's maximum value). I have not found re-flashing with calibration only would re-set my LTrims. I always used the Scan Tool calibration tool to re-set.

Let us know how it goes. I would be intrigued if you got it to work by a different method.