chrismcdaniel

iTrader: (14)

after the new motor went in, we had some problems getting it to idle (408 A4+Big Stall)

Once we got it to idle, it was running WAY to rich. We scanned it, and saw that on bank 1, the the fuel trims where at 25%. We reset the fuel trims, then it idled PERFECT.... even while in gear!!

after a few minutes though, bank one fuel trims went back to dumping 25%... the O2's are switching fine, the numbers are kinda high though (700-900)
My guess would be the 02's, what do you guys think?

any help would be great!

gametech

iTrader: (1)

I would guess one cylinder is skipping. The unburned air causes the o2's to read lean, causing the pcm to dump fuel, causing the other cylinders to run rich. I'm guessing big stall means big,lopey cam, so you might not notice a cylinder skipping at idle. This is of course just a guess.

GOaT Cheese

If your fuel trim is at 25% then you are running lean, the PCM is adding fuel to try and compensate. If the fuel trim was -25% then it is a rich problem. Try unplugging your MAF sensor and see what the fuel trim does. If the trim cleans up, look real close at the sensor itself. If the trim stays at 25%, then its back to square one.

chrismcdaniel

iTrader: (14)

Its a SD tune, no MAF.

im possitive the plug wires where all connected, and the plugs are all new. i wasnt getting any midfires on the scan.. The came is HUGE though, so it does run rough at idle.

also, its only happening on one bank.

GOaT Cheese

Then nevermind the MAF trick.

chrismcdaniel

iTrader: (14)

Thanks anyways man

chrismcdaniel

iTrader: (14)

Ttt...

Black02SS

iTrader: (36)

If you are seeing them peg at 25 on only one bank, I would check for a vacuum leak somewhere. It could be around the intake or one of the vacuum lines on the back came undone.

chrismcdaniel

iTrader: (14)

thanks, that sounds about right.. with this vic jr intake setup, i have been affraid of vac. leaks, but i did think i didn have any.. but i will definatley check again.... but could you explain why it would only effect one bank?

thanks,
chris

Black02SS

iTrader: (36)

Basically the motor is two halves. If you have a leak on one side, then you will only notice it because the O2 for that side notices a lean condition due to the extra amount of air and tries to compensate for it, hence the +25 trims.

chrismcdaniel

iTrader: (14)

cool, thank you. that makes makes sense to me. ill check everything again tomorrow.

98 Raptor TA

iTrader: (9)

i had the same problem and it was a leak at my header collector. Check for exhaust leaks or intake (vacuum) leaks

chrismcdaniel

iTrader: (14)

this could be my problem, i have slip on merge collectors..

Lrry93

iTrader: (2)

I have been helping Chris with his car and I am stumped. Here is the update as of today.

The car will run with both banks locked at zero until it warms up and then bank one runs lean all the way to -15.6 and stays lean. Bank two stays locked at zero. We set up a misfire scan and read zero misfires even when we unplugged a wire from the coil packs. We also changed the O2 sensor with no change. There were no vac/ or exhaust leaks found.

Any ideas?? Injector or coil packs bad maybe??

Black02SS

iTrader: (36)

Switch the plugs/coil packs from one side to another if you think that is the problem. I still suspect there is a leak somewhere.

Black02SS

iTrader: (36)

They will stay locked at 0 until it warms up as it is in open loop.

Lrry93

iTrader: (2)

The only thing that I could even think might be causing an issue but dont see how is that the PCV valve is open to the air instead of being plugged into the intake and its not grounded and the other side for the fuel system is open to the air as well.