P0302 misfire cylinder 2

KENT HASSELL

MEMBER
2003 PONTIAC AZTEK
3.4L
6 CYL
2WD
AUTOMATIC
108,000 MILES

Vehicle just had major tuneup including all ignition coils. We also replaced the fuel injector on cylinder 2 and it did not help. Maybe electrical to the fuel injector? The compression is excellent, around 130. I think it uses a little more coolant than normal (i run the ac a lot), but a leaking head gasket is likely not the problem with that kind of compression. I do not see any leaks. I used sea foam in the gas last night, a full bottle for 16 gallons. I t stopped the rough idle, and motor did not break up on a 30 minute freeway drive. I jumped on it on the freeway coming home from about 65 mph to 80 mph and the service engine soon light flashed for a few minutes and went away. Then on a side road I really jumped on it and the "service engine soon light" stayed on. It did misfire when jumping on it, but still a lot of power.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

A leaking head gasket could cause the problem and not effect the compression. Here is a guide to check to see if you have a blown head gasket or not.

https://www.2carpros.com/articles/head-gasket-blown-test

Please run this test and get back to us so we can continue helping you.

Best, Ken

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Wednesday, March 29th, 2017 AT 12:05 PM

KENT HASSELL

MEMBER
2 POSTS

Hi Ken,

I think we are on the right path here.

I do not believe it is the head gasket, however it could be, or a warped head. My brother Tim was a mechanic in the muscle car era and use to race cars at National speedway, in Riverhead NY. Of course cars are different to some degree today.
We believe it is a different problem, maybe 60-70% chance, I think 90% chance. The 2003 Pontiac Aztek had a defective intake manifold gasket based on the material it was made of. I believe it was some kind of plastic. The original owner was probably not aware of the factory recall that expired. The new gasket is made of a different material.
Is it possible that the lower intake manifold gasket is allowing coolant to get into the cylinder? When I first bought the car it had excessive white smoke when starting from cold. Tim said it has some water (coolant) coming out of the tail pipe that someone said was normal, but he disagrees. The misfire shows as cylinder 2, PO302.

I saw this statement on the internet, but not sure if it pertained to my vehicle;
The coolant flows through the intake manifold to the cylinder heads to reduce engine temperature. Expansion, contraction, and heat from the engine cause the gasket to fail.
This will cause coolant passing through
the intake manifold to leak.

Maybe this is an internal leak?

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Wednesday, March 29th, 2017 AT 10:24 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

O yes, now that you mention it I have heard of that problem as well. That would be a great place to start.

Please let us know what happens.

Best, Ken

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Thursday, March 30th, 2017 AT 3:12 PM