This was from my thread about ILLS disappearing. I asked if the issue sounds like fuel delivery, when it only happens when the tune is loaded, and goes away when the car is on stock tune:
Absolutely!
that is an excuse many people use to blame the tune itself, when they dont really understand the process and what occurs.
A car with a PIG RICH stock fuel table will not detonate.
Once the fuel table is leaned out to a performance level the car WILL detonate IF the fuel system isn't keeping up.
If you command 10/1 AF stock, and the fuel system is weak the car will/could deliver a 12/1AF instead of 10..
The car runs great because of this.
BUT... if you command a 12/1 AF and the car has the same TWO FULL POINTS of AF "variance".. then the car has issues because it's NOW running at 14/1 AF and PINGS or detonates.
it's called the "variance" between "commanded and delivered" A/F ratio.
it's a common occurance once the fuel pump begins to "give up".
this is where tuners and customers often have problems.
Tuner sends performance file, car detonates
Customer returns to stock..detonation dissapears
Customer blames tune/tuner.
Tuner who isn't required to educate the customer doesnt respond.
I had the exact same problem, with a chip car pings
without a chip it ran GREAT!
problem WAS the fuel pump, so I'm speaking from personal experience with an issue that I had..
same deal...
and I was WRONG for blaming the tuner, but that was almost 10 years ago.