Questions and Answers

GMC Sonoma Pickup Running Rough Q. Vince, I've got an 1988 GMC Sonoma Pickup. It's got a 2.8 liter V-6 with power steering, automatic transmission with O/D, A/C, fuel injected. The truck had been stored for about a year in my garage, but started occasionally. After bringing it out of storage, I changed the oil, and drove it for a couple of weeks, and it ran fine. Used up the gas that was in it, and filled it up.

I needed to get it inspected. As I was driving to the garage, it started running rough. I returned home, and checked for stored codes, nothing. Before I headed to the garage, I aluminum taped up some holes in the tailpipe. Could the additional back pressure on the engine have caused some problems?

I also re-gapped all of the spark plugs. If I damaged one of them, could it run okay for a while and then have problems? I've not removed them all to check, as they can be tricky to get out on some cylinders.

Any ideas would be helpful...

A. You may have cracked a spark plug while cleaning them. If it's missing on one cylinder you need to cancel them out one at a time to see which one it is. This would require you to start it up, put the parking brake on and have someone sit in it with a foot on the brakes. Then pull the plug wires off one at a time to see which cylinder is not dropping any RPM's. Could be a plug or a wire or even a cracked distributor cap.