Re: Service engine light??

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Posted by OnBelay ( on 07:35:39 02/21/13

In Reply to: Service engine light?? posted by Guy

: '99 GMC Sub,K2500,454,3/4 ton, 4wd,auto trans, ac, nearly 200K on the girl.
: SES light comes on occasionally. Stays on for a few days then goes off. A buddy put a scan tool on it and got a "random misfire" code.
: It happens when its cold for here. Say 20 or below (I know that's not cold).
: Any thoughts or experience on what might cause it to throw the code?
: Thanks
: Guy

Sorry to give you the smarta$$ answer, but....

I'm pretty sure you have a random misfire.

Check, in this order:




My best guess would be a plug that is slightly fouled or has a crack.

You don't really give enough specific. "Occasional" to some might be every six months, and to to others might be every 6th time you start the engine.

A true scan tool (not just a code reader) will give you access to a misfire counter, so that you can check the history and hopefully find which cylinder.

So, it becomes a question of "how bad do you want it to stop?"

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