Misfire issue?

CRAIGAK

MEMBER
2004 OLDSMOBILE BRAVADA
4.2L
6 CYL
2WD
AUTOMATIC
99,000 MILES

I developed a misfire on cylinder #2 according to OBD2 error codes and I replaced all the plugs because it needed that anyway, but that made no difference. Then I swapped the #3 coil, which is pretty new, with the #2 coil and the specific error code P0302 went away, but then I got a P0300 general random multiple cylinder misfire. Could switching those coils have something to do with that? Also, I have 5w-30 oil in this car and I am in a hot climate (west central Florida) and someone told me that I should have 10-w30 in there and that it might, even though it's remote, cause the P0300. I don't think that's true though. Am I mistaken, or is he? Thanks.

Craig

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,574 POSTS

Yes, it sounds like you need a set of coils which is common, the engine oil will not make a difference on the misfire issue. Also, you might need a MAP sensor and to change out the fuel filter. I would also clean the throttle body, here are guides to help with instructions in the images below:

https://www.2carpros.com/articles/throttle-actuator-service

Check for a vacuum leak when the engine is cold only.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Check out the images (below). Please let us know what you find. We are interested to see what it is.

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Tuesday, November 1st, 2022 AT 10:46 AM

CRAIGAK

MEMBER
29 POSTS

Thank you. I will start with one possible solution and work my way through them. I don't have enough money to get everything mentioned right now so it will take a while to eliminate each item as the cause until I hit upon the right one. I appreciate the help. I will update you when I find out what caused it. Thanks again.

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Tuesday, November 1st, 2022 AT 11:14 AM

CRAIGAK

MEMBER
29 POSTS

Hello. Sorry it's been so long. A lot happening. Well, it turns out it was a bad coil. Originally, the misfire was on cylinder 2. I swapped the coil with the one on cylinder 3, and the misfire continued, but I did not get the single cylinder misfire code but the general one as I said. I had a hunch and replaced that coil with a new one and the misfire was gone, along with all the error codes. Tests for codes are coming up clean now. Thanks for the help.

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Wednesday, November 16th, 2022 AT 7:58 AM

KEN L