Back during the winter our 04 GT2 started having a misfire or skip of some kind after 170k miles or so. At first I thought it was a transmission problem, but turned out to be something engine related without any codes triggered. Our mechanic said maybe it's the ICM, and not knowing enough about how it all works I thought a cheap ICM from Autozone would help. We have the same PCM. The car just ran worse, with it dying and undriveable around town.
I could pedal it like a dragster, and get it to the GM shop where they flashed updated software. I don't know if they flashed the PCM and ICM, or just one module or the other. It still had a skip or intermittent hesitation at part throttle so we had new iridium plugs and Bosch wires installed. It still had issues, with P1361, P1362 codes now tripped, and even a P1106 once or twice. We decided to get a grocery getter and leaving the GP sitting until Spring so it could warm up outside, and my ailing back could get better.
It was nice outside yesterday, and I decided to start the GP. I opened the hood, removed the plastic engine cover, and it fires right up, but I start hearing something funny. Sticking my head under the hood, I hear crackling and popping like arcing high voltage, but cannot determine where - seems like a front plug wire, but not sure. Damn! I wish it was dark outside. Starting the car again in the dark, there wasn't any arcing or popping, or anything funny. It started and ran fine.
I wonder if there's a bad coil, or if it was the routing of the plug wires causing something. I'm going to route them better than the shop did, and am also thinking of putting the original ICM back on. I'm also tempted to get a PCM from the junkyard, and maybe some coils. This whole thing is kind of baffling. Suggestions are appreciated, thanks!