Good afternoon all, Just recently I got the GMS1 sensors and had a street tune done with HPT. Car is stock except for a ZZP Intercooler and the K&N CAI and now the sensors. Boost was turned up to 25 spike tapering down to 22. I don't have an AFR gauge however so I'm almost positive my AFRs are garbage. Pulling in second every now and then I have this issue. I'm pulling, boosting just fine, then at about 5k the exhaust just sounds like garbage, I lose my power, a lot of crackling, shift to third gently and the problem goes away or take your foot off the gas and back on and it goes away. It did this even before the tune and the sensors as well but normally at redline from 2nd to 3rd. Anyone shed some light on this issue possibly? All help would be appreciated. Car is a 2009 Cobalt SS.

 

Plugs gapped appropriately? Had the intake valves cleaned recently? I have seen misfires in that range, too with a Trifecta 21psi tune. Since cleaning the valves and changing my intake filter setup, it's been flawless. Plugs have 30k on them now, I think.

 

 

How many miles on the engine? They are probably overdue. It's not that hard to remove the intake manifold and clean the valves with something like GM top engine cleaner.

 

thats plug gap issue for sure. just fix that issue with a locals car. closed the plug gaps too .029 and it pulls like a train. give it a shot.

 

 

Last time someone mentioned something like this it was injector seals failing. direct injected, so you have to take the intake manifold off to get there anyway. then you can see how bad the valves are.