Hey all so i have a 1998 c5 with 70k on it and i have been trying to tackle this certain issue for a while now. i have codes P0351 and P0353 ignition coil primary/secondary circuit for coils A and C. the car runs perfectly fine on a cold start in the morning for my drive to work. however after the car sits after a drive (even just for 5 minutes) or i am stuck in traffic the car will make a rattle or pinging sound only under acceleration not while revving and on occasion it will run very rough and will set these codes. i have replaced all coils, plugs and wires and even brought it to the dealer where they were just trying to throw parts at it and replaced all of my plugs, wires again and 1 coil (only when P0351 was present, P0353 came up recently). it seems to me that it is heat related and i do know that heat causes resistance so i wonder if it is a wiring issue at this point. if anyone has any clue it would be greatly appreciated thank you.

 

Welcome to the forums. Sorry for your frustrations, it looks as if you have the obvious repairs. That leaves the igition coil circuit or PCM. Next step would be to check the wiring and connectors up to the PCM and the connections on the PCM. I have used WD40 on connectors and had good luck. If you have no luck there you might need to check into a different PCM or have that one sent in for service and checked out with the heat issue which is common with a cracked solder. Good luck.

 

Welcome to the forum. Good luck with your investigation and repair.

 

Try and check as many ground connections that you find. I noticed on Amazon the wide variety of contact sprays on the market today for wiring connections. I wouldn't rule out the wiring harness condition and contacts on the backside of the fuse box or fuse itself. I could be way of base but it's something to think about. The fact that it only affects one or two cylinders when its warm makes me think wiring connections or ECM.