Owner of a 2003 Z06 contacts me that the car runs like crap.
His tuner cannot figure it out
He sends me the PCM flash, the tune stinks but not the cause of how bad the car is.
I had him do a drive with Ease scanner recordings and email it to me to analyze
You spot right off that engine stays in OPEN loop
Look at the sensors that dictate which loop, TPS, MAF, temps and MAP and they are good.
Stuck in OPEN loop and notice fuel learn stays OFF, fuel trims super lean and so are values from O2s. Bigger clue is short term fuel trims locked at zero.
Simple then to know what was wrong so I told them to measure fuel rail pressure and sure enough instead of being 58 PSI it was 24
You'd think that forum supporting vendor tuner would have seen this ASAP rather then owner having a down car for over a week and it took me less then 10 minutes, 2,400 miles from the car to find the problem
To make it even worse the tuner instead of solving the problem turned off the LEAN and RICH error codes so they would not trip so owner then would not even know how lean the engine was.