altitude or air density

[jcp240z]

The ECM has a pressure sensor built into it that is used to compensate for altitude.

[bcredliner]

What symptoms of a problem are you experiencing? any error codes?

[1iwilly]

quick re-cap back in june head gasket was done all new seal were install
but was getting p2096&2098 no vacuum leaks at all.
then the other day i started the suv with the maf plug disconnected
then when i got the transfail i re-connected the plug clear the code started the suv and both LFT were reset to 0.0 since then no more SES light but the LFT ARE IN THE 2.3 AND 3.8 while driving stop and go.when on the highway b-1 LFT=0.0 LFT B-2=2.3 bank 1 sensor 2 stays in the 740 to 745 where bank 2 sensor is 680 to 720 fluctuating a lot back and fourth where bank-1 sensor 2 stays more in the range.740-745

Originally Posted by bcredliner

What symptoms of a problem are you experiencing? any error codes?

[bcredliner]

Those are measurements. Symptoms would be things like lose of power, missing, starts hard, stumbles etc.

[1iwilly]

no symptons at all well only the rough idle when in drive only.
and i just would like them be more closer to specs.0.0 to 0.7

Originally Posted by bcredliner

Those are measurements. Symptoms would be things like lose of power, missing, starts hard, stumbles etc.

[bcredliner]

Originally Posted by Riggodeaux

Lots of amateur comedians here, willy. Terminator might be getting to something, though - is there an altimeter or similar control that might have your fuel mix out of wack, even if its not related to leaving the comforting environment of Disneyworld for the beach?

I guess that means your avatar is a portrait of you.

[Riggodeaux]

In an amateur sort of way, absolutely!

[bcredliner]

Fuel mixture is controlled largely by the MAF and pre cat O2 sensor regardless of the altitude. However, when the altimeter and MAF readings do not match it can result in no adjustment to fuel mixture resulting in a variety of engine symptoms. The variation in air density and altitude on your A to B trip is well within min/max fuel mixture parameters of the MAF/pre cat O2 sensor and any mismatch between the altimeter and the MAF would not be significant enough to matter in your circumstances anyway.

I don't think the variation on bank 1 has anything to do with the MAF or the altimeter as the variation would be in both banks. I would troubleshoot the pre cat O2 sensor on bank 1 as the culprit.

[1iwilly]

thanks but wouldn't be bank-2 precat 02 since the reading LTF reading is in the 3.8 compared to bank-1.?? i might just keep an eye on it for now until i put a few more mile for the computer to finish doing it's adaptation mode.
today i re-tighten the intake manifold screws they took an extra 3 turns each
and bank-1 is LFT=1.5 bank-2 LFT-3.1 once again thanks for the breakdown explanation.

Originally Posted by bcredliner

Fuel mixture is controlled largely by the MAF and pre cat O2 sensor regardless of the altitude. However, when the altimeter and MAF readings do not match it can result in no adjustment to fuel mixture resulting in a variety of engine symptoms. The variation in air density and altitude on your A to B trip is well within min/max fuel mixture parameters of the MAF/pre cat O2 sensor and any mismatch between the altimeter and the MAF would not be significant enough to matter in your circumstances anyway.

I don't think the variation on bank 1 has anything to do with the MAF or the altimeter as the variation would be in both banks. I would troubleshoot the pre cat O2 sensor on bank 1 as the culprit.

[admranger]

What's the acceptable range of fuel trims? This could all be normal...or not.

I'm with bcred here. MAF or pre-cat O2 sensor(s) if it is a problem. Or perhaps you were getting air leakage and you resolved that by turning screws.

For the record, the partial pressure of oxygen decreases at altitude. Nothing gets 'thinner' at altitude with the possible exception of the ski "bunny" at the bar after your 9th beer.