Hello,
I just bought a 2006 Grand Prix GT from a friend that got a new car. I noticed that it is misfiring bad at idle and up to speed. 3500rpm gets real rough them smooths out.
If I set the cruise, when going up a hill, the car will try to accelerate but then stutter real bad and the check light will blink on and off for about 5 seconds.
I had the car scanned and bought an OBD2 scanner. P0300 is the only code I get. I checked the live misfires and its only one cylinder 3.
I noticed that someone had wrapped electrical tape on the spark plug to #3. Found a cut in the wire.
Replaced the plug wire with another stock AC Delco wire. Still missing on 3.
Checked the coil pack on 3. The pack was producing a dirty red spark.
Replaced the pack and it now has a nice large blue spark. Still missing on 3.
Replaced the spark plug "which looked fine" with ACDelco 41-101 plug.
Had a compression test done on 3 which was within specs. Still missing on 3.
Used a couple cans of carb cleaner on vacuum lines checking for leaks. Didn't find anything.
I even replaced the injector for the fun of it. I noticed that the bottom of the injector, below the lower O ring was cracked. New injector in but still missing on 3.
I replaced the battery which tested bad with a new one.
I am wondering if there is a good way to see if the catalytic converter might be the issue, or a good way to see if the head gasket is leaking. Or a test I can do on the ICM. Other than that I cant think of any other thing to test. I am hoping someone might be able to point me in the right direction because I have exhausted my knowledge.
Thanks.
