Sorry, I posted this in the wrong spot. I took the car into a Chevy dealership, and they said that the diagnosis onboard code said it was misfiring on Cyl. #2 and #5, and they said that it was from an ignition module failure. The car only has 49k on it, and it's been given oil changes every 3,000 miles, and all the anual service and maintenence it was supposed to have. In the other one I posted Mad Mike said that "a little maintenance will go along way", I was just wondering if there is some kind of maintenance that I forgot to do. I've sent a couple bottles of fuel injector cleaner through the last 3 tanks of gas, and it hasn't helped any.

Does anyone know if it's possible the igniton module is only affecting two cylinders, what other possiblities could there be? Any suggestions?

 

spark plugs and wires, fuel filter, differential fluid, trans fluid...

maybe you have a bad coilpack? or a moisture buildup?

 

There is little maintenance you can do to an ignition module itself, except keeping the electrical connections clean & dry. Being that only cyl #2 & #5are misfiring, most likely the ignition module is good and the 2&5 coil is bad. A bad ignition module would show up as multiple random misfires, rather than individual cylinder misfires. There are two versions of coil packs, one with 3 individually mounted coils, and one with 3 coils moldedina single unit. Either way the coils plug in on top of the ignition module and are held in by screws.

 

Thanks Pete. The computer did show that it had random\multiple misfires, and I think they did further testing to determine it was on those cylinders. Do you know what makes modules go bad?

 

Basically they are a piece of electronic equipment, and are subject to failure due to high heat, vibration, quick temperature changes, and the detrimental effects of high voltages. Under the hood is not the best envirnment for electronic equipment, and it is surprising that they last as much as they do.

 

mine was misfiring on cylinder 4, so I replaced the spark plug and tested the coils. Everything checked out good but my check engine light was still on for about a week or two after before it turned off.

 

Wow, I got the ignition module, and was getting ready to install it. Once again, the dealer used the tools to determine it was missing on cylinders 2 and 5. So they wanted to charge me $400 for the part and labor. Got the part, and I left it running and opened the hood. Sure enough, I had a spark that was arcing off cylinder 2, it just took three weeks to be really obvious. So I replaced the wire, and it runs at 100%, so if your having problems, I would recommend checking the basics first, even if it doesn't look look like an obvious problem. I wish I would have.

 

You must have forgoten that little bit of maintenance

 

lol, how often are you supposed to change the spark plug wires? My car only has 45K on it.

 

You would think they should last longer than that. Maintenance schedule telss you to inspect every 30,000 miles. But the schedules also say replace plugs at 100,000 and I got many vehicles around 75,000 with missfire codes that just needed cap, plugs and wires.