2003 Pontiac Grand Am P0306 Cylinder 6 Misfire

SOUNDPROOF

MEMBER
2003 PONTIAC GRAND AM
6 CYL
FWD
AUTOMATIC
88,500 MILES

I just returned from a 1800 mile road trip and the car ran great. The day after I returned home, it started running really rough while at idle or parked and the Service Engine light was flashing. I hooked it up to a tester, received P0306 Cylinder 6 misfire detected. I replaced the plugs, wires, and coil pack, still having the same issue. It has died once while sitting in park and then it did not want to start after that. It finally started but it is still running very rough. Any ideas?

3 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

Start with a compression test to rule out headgasket or intake gasket.
The 3100 and 3400 had there share of intake gasket problems. If compression is low on #6, see if GM will replace intake manifold gasket under recall.

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Saturday, August 29th, 2009 AT 9:21 AM

SOUNDPROOF

MEMBER
2 POSTS

Took it to a shop, mechanic said the compression was fine and even the resistance in the fuel injectors seemed to be OK. However, he said he was 80% sure it was the injector for cylinder 6. I gave him the OK to replace it, costed $433.00. Runs great now, no issues.

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Saturday, August 29th, 2009 AT 9:28 AM

MMPRINCE4000

MECHANIC
8,548 POSTS

Great news!

I would also add a can of a product called "SeaFoam" to gas tank two or three times a year.

This will keep injectors clean and will also stabilize gasoline, preventing the formation of varnish.

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Sunday, August 30th, 2009 AT 8:38 AM