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Help! 2004 Grand Prix GT misfire

Scott Gerhart

Scott Gerhart

New member
I had a coolant leak and unfortunately had an emergency to go to and limped the car there while overheating. Worst possible timing. Coolant leak fixed and now the engine has a very slight misfire only while idling. My mech buddy said it might be a bent connecting rod. I'm trying to explore all possible options before I would just replace the motor. He checked the valves and they looked ok. It's cylinder 3. Any ideas?
 


Do a leak down test and compression test on cly 3 and all the rest if your gonna do it. Make sure you didnt warp something or pop a gasket first
 
Did a compression test and cyl 3 was only slightly lower than the others. Replaced plugs and wires. Any O2 sensors or the MAF sensor that could cause it? Trying to think of stuff that could be simple. Clogged injector? It got really hot. Maybe a hole in the intake manifold? That's plastic
 
This may sound really stupid but remove your air filter housing and inspect the insides fully for excess trash, leaves, plastic shopping bags, etc. I just experienced a rough idle and a misfire on cyl #2 (P0302 code) --- I found 2 plastic shopping bags sucked up into the front of the air filter housing and they had about 40-50% of the airway clogged up. Removed the plastic bags and put it back together. It seems as though the problem is solved. It won't hurt anything to check it out and clean it while you have it out. This very well could be your problem.
 
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