55 Chevy with LS2 high fuel trims

[HRD]

I'm working on a custom 55 Chevy with a basically stock LS2 from an '05 GTO. The car seems to run ok, but occasionally sets lean codes (both banks) while operating under cruise and idle conditions. I logged some data while driving arround town and found some very high LTFT's. I believe the tune is not far from the stock GTO tune. I've checked for vacuum leaks and checked the fuel pressure (60 psi). The car is using the Corvette filter/regulator. We recently installed a new one just to be safe.

Any suggestions?

[LazMan]

Wow. Those ARE some crazy fuel trims! The O2 crossovers are so JUMPY!

I owned a 2006 GTO for a number of years (have a 2009 G8 GXP now) and did countless logs on it - I just looked at one and it was not at all as jumpy as yours are.

The tune looks ok for stock ... so the question back to you is this: is your set-up approximately like a stock GTO? (Stock exhaust manifolds and stock O2 sensors as compared to an 05/06 stock GTO?)

If (from the look of your Engine Diag tab vs Stock) not (i.e. if you are running headers and/or some other O2 sensors) then that might be the root of the issue.

Let everyone know and I'm sure a solution can be found.

[HRD]

Running shorty Street and Performance headers, but otherwise the engine is stock with stock O2 sensors. I am running a push in breather oil filler/breather that I realize will let in some unmetered air through the PCV system, especially at higher vaccum. I wasn't expecting it to have this much effect.

Thanks

[LazMan]

Shorties are no problem. Unmetered air tho - that creates all sorts of weird issues with fuel trims! Sounds like you are on the right track. Taking care of that most probably will solve your issues.

Good luck with your sweet ride!

[HRD]

Hey thanks for the help.