‘96 Corvette Negative Fuel Trims. Help!

[NomakeWan]

I was always under the impression that when O2s fail they fail lean? Causing the pcm to add fuel (blm above 128 for safety). They are switching but they have been moved I think so may need to tune for o2 delay and such.

either way it’s at 108; -16%, soon as CL kicks in.

i believe it’s false because throttle response become immediate trash but if I force open loop and clear blms the throttle response is snappy.

If the O2 circuit fails, then that may be how the PCM compensates; but if the circuit is good then the PCM will trust whatever the O2 sensor is telling it, including if the O2 sensor falsely reports a rich condition. I've seen it happen.

If the O2 sensors are not in the stock locations, then yes, it's also possible that you'll need to change the appropriate sections in the BIN. That being said, was this something it always did since the swap (and/or the moving of the O2 sensors) or did this just suddenly happen for no apparent reason? That should help narrow things down.

[johnny_b]

The o2s have been like that since I bought It. I will adjust the tune for that. Kinda doubt that’s causing max negative fuel trims but It can’t hurt.

im trying to avoid band-aiding the problem through tuning

[NomakeWan]

If they've been like that the whole time, but the trims only started acting up now, then there's no reason to suspect the location of the sensors to be the culprit.

[johnny_b]

If they've been like that the whole time, but the trims only started acting up now, then there's no reason to suspect the location of the sensors to be the culprit.

as far as I know the trims may have always been messed up. That was the reason I converted to obd1 as I’ve tuned several obd1 lt1’s. I’ve been using the data logs to point me to things like the leaking injector and the regulator.