Earlier today I drove my 98 Jimmy (after it was parked for about 2-3 days) and noticed it wasn't running very good especially at low RPM's and idle. It was obviously a misfire. I drove it around the block and parked it...CEL came on. Turn it off, turn it back on and start driving to the nearest AutoZone for a code scan. Truck is running fine after 2nd start up, no stumbling, no issues when stopped. Got to AutoZone, code scan: P0306 cylinder 6 misfire. Drive out of the parking lot and the light goes off. I get all the way home with no issues.

Recent replacements:

Plugs, cap, rotor all AC DELCO. New wires. New fuel filter. New front Denso O2 sensors.

Just moved from Michigan to southern Illinois, about 8 hour drive. Filled up and did Seafoam treatment the morning I left. Got 21 MPG with a ton of crap loaded in the back.

Truck has always had a SLIGHT stumble at idle, I suspect that the spider injector will need replaced at some point.

Anyway, I know the symptoms of a P0306 but am curious as to what would cause a cylinder 6 misfire only for a short time? I've read a lot of threads on them but almost all the people have issues with a cylinder 6 misfire that won't go away. Anyway, thanks for any info.

 

Just because the tune up is all new doesn't mean you can rule it out, Make sure a wire didn't come loose or rub threw on the engine somewhere, check the spark plug for cracks proper torque and gap, check the cap for debris or cracks, if all checks out then start looking at things like vacuum leaks, or intake manifold leaks carbon build up, bad injector etc

 

It happened again. This time, the check engine light blinked a few times. I parked it, restarted it a few times...problem still persisted, drove off and within a mile the problem went away. I would figure if any of the tune up components were bad, it wouldn't fix itself like that. I'm leaning towards the spider assembly. This thing has 200,000 miles and still running the stock injectors. Any other input or suggestions would be greatly appreciated, though.

 

Update: new Delphi injectors finally came in. Replaced the stock unit and no more issues!