Diagnose P0304 code

FRIEDA LETSOM

MEMBER
1999 PONTIAC MONTANA
3.4L
6 CYL
2WD
AUTOMATIC
173,627 MILES

I had a P0440 on about a month ago. When it was read again P0301 came on. Cleared codes and changed fuel cap. P0304 came on and was told it was the ignition coil. Changed spark plugs, wires, and the coil for 1/4, and 2, 5. 2 days ago CEL came on with P0507. Cleaned the IAC. Yesterday added CataClean on 1/4 tank of gas and drove 15 miles and noticed my RPM's were going up with acceleration. Filled my tank and still seemed fine. Then on my way home RPM's not going up again and CEL flashed. P0304 came on again. Then tapping under the hood. Not sure what is going on at this point.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
42,861 POSTS

Hmm, not a big believer in gas additives BTW. The codes is for #4 cylinder is having an issue. Lets remove the spark plug to look at it to see if it is black? Also lets do a compression test. Here is a guide:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run down this guide and report back.

Cheers, Ken