Fuel trim jumps to -100%

[mysunnshine]

Has anybody else experienced the STFT correction go to -100%? I'm trying to tune my 6.0L and during steady state it goes along well and then like a light switch the STFT pegs to -100%. I have STFT and LTFT off in the calibration, the closed loop temp set at 999. Any ideas?

[joecar]

It looks like it transitions from VE to MAF, or vice-versa, and either table is way different (i.e. produces way different airmass/cylinder value than the other table).

Or, if you're running VE only, then it might have a large step (large enough for the PCM's interpolation to produce a large value compared to previous value).

[mysunnshine]

For this log, I was SD only. I had already attempted to tune MAF only but had the same issue with the engine shutting down. I don't understand what you mean about the interpolation? Do you mean a smooth VE map with no drastic steps? If so, it's all a smooth transition thruout the map.

[joecar]

Yes, smooth(er) VE with no big steps.

Hmmm....

post some more logs, and tune current file.