Bought a 03 z06.owner said it has a lingenfelter cam,no cats.cold air intake.8500 miles..it also has headers.and i had billy boat bullet exhaust installed.also owner said it had been tuned.after i put the bullets on it sounded great when you backed off it.it would back fire once in a while.took to a local shop.he checked it out and it scanned running lean..still ran good and fast..now when i punch it,it sounds like its missing and back firing..is that because its lean?can it do damage? And how do i correct..any help greatly appreciated..

 

With all that aftermarket work done to the engine, a GOOD TUNE needs to be accomplished. It needs to be accomplished by a tuner that knows how to properly tune the PCM.

The tuner that did the tune prior to you owning the car is an UNKNOWN. Your current tuner says "THE ENGINE IS RUNNING LEAN" Is it running RICH/LEAN because of a poor tune OR because of something you changed or something that happened to the engine?

Lean is NOT good. How lean and where is it running lean??????????????
Is it lean in the CLOSED LOOP operating mode or the POWER ENRICHMENT WOT Mode???

There are something called a Long Term (LTFT) and Short Term Fuel Trims (STFT) table. The PCM logs AFR DATA and that data and makes changes to the fueling table as a result of the LTFT Averages. IF, the tune is good and the engine is running correctly, the LTFTs should be ZERO % to slightly negative. They can go as high as +/- 25% but,,,, the more that they are off of ZERO % it negatively effects your POWER ENRICHMENT AFR.
If you have a +20% LTFT AFR when you go into PE Mode the PCM ADDS that percentage directly to the WOT PE table and makes it that much % richer. Running very rich in PE is safe but you don't make all the power that you could if it was the correct PE AFR. If the PE AFR is LEAN, you risk Cylinder/Piston damage due to detonation. SPARK KNOCK. LEAN IS NOT GOOD!!!

All of this can be sorted out by doing something called a DATA LOG. The tuner or anyone for that matter that has tuning software can data log the PCM and tell you how the engine is running and what needs to be done to correct the issue.

Bill

 

Bill, Thanks for all the info. Not quite as versed as you are. Wondering if you know a good tuner in the Phoenix area. Would like to show him your thoughts. Want to fix this before I tear something up. Thanks again for the wealth of information.

 

I don't know anyone in that area. Someone here may and be able to point you in that direction!

Before you let anyone tune your PCM, you need to make sure that ALL the Engine sensors that provide data to the PCM to allow it to calculate the proper AIR/FUEL/SPARK are working properly. A good tuner can tell you that.

After that is sorted out, then get the proper tune.

I AM NOT A TUNER but,,,,, I know a little about how it all works and have tuners that I trust to do the tuning.

Bill

 

Clean the MAF asap