So I bought my Grand Am a few weeks ago. Dealer replaced something with the EVAP system and put a new cat on the car. Now I have a problem with WOT detonation and hesitation. If I put my foot to the floor she down shifts and rpms go up. But I can hear it detonate (popcorn sounds) then rpms drop, hesitates and rpms go up and keeps doing it until I take my foot out of it. Now, normal driving it's flawless. Half and 3/4 throttle it doesn't do it as much. I get the SES flashing for misfires. I replaced the plugs with ACDelco iridium plugs and Delphi wires.
I'm thinking with 86k miles it might have some carbon build up and I'm running 2oz of Marvel Mystery Oil in the gas. I've thought about seafoaming the top end. The EGR might need some cleaning. But I'm not sure. Do you guys have any idea's what the crap is the problem?
I'm thinking with 86k miles it might have some carbon build up and I'm running 2oz of Marvel Mystery Oil in the gas. I've thought about seafoaming the top end. The EGR might need some cleaning. But I'm not sure. Do you guys have any idea's what the crap is the problem?
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