Tune wont hold

[kurupt305]

So look I tune my car and that day we tune it to lets say 11.0 afr it will drove like that just fine but the next day car tune will change and the afr will lean out at top of rpm for instance 5k and up it will go to 14-15 afr lets say tune is fine what other reason could this be happening ? Bad maf? Bad fp? Not enough volts to fp? Maybe I should go back to stock pump or find another lq4 ive had different tuners mess woth this tune and same symptoms occur not sure how a tune can change on its own maybe bad pcm?

[Iceman6669]

Could be fuel pump.

[kurupt305]

Ive swapped fuel pump twice but what happens in my 05 gtp is voltage fluctuates due to a internal voltage regulator where it only kreps voltage high if theres a high power demand

[Fivefingerdeathpunch]

Not the tune or PCM, this is something else.


Simple check but if it's leaning out super bad then maybe dangerous, if in the scan the commanded AFR never changes or still says close to whatever you are commanding then it's not the tune. More than likely it will still always say and I'll just give a number here of 11.5 afr cmd, so then you know where to look.

[kurupt305]

So I should command 11.5 at wot? And if its at 10.0 which its at now what could it be zzp says the pump is scavenging to put in a 06 fp canister I was going to try and swap in a spare 07 stock canister and see if its a voltage issue being my 05 dc volts vary from 12.5-14.8 apparently 05+ grand prixs are all the same which sux because my aem fp requires 13.5 at the pump at all times