99 Explorer, Missfire

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Apr 9, 2007 | 06:24 AM

JJSammy

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Joined: Oct 2002

Posts: 3

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From: Santa Rosa Sonoma

99 Explorer, Missfire

I have a 1999 ford Explorer with a 4.0L motor. The trouble I have is cylinder #3 miss fires, but only for the first couple minutes. Then it clears up. I've changed plugs, wires checked compression etc. The problem will begin with a check engine light and the code will be a misfire cyl #3 .

I remove the plug and it threads out snug. not stripped just a snug fit. Once the plug is in hand it appears as if the back portion of the threads have carbon build up. The plug threads in the head about 1/2 " but the seat is closer to 1" ( So the plug has 1" of threads then the tappered seat.)

After the cleaning the threads and re-installating the plug the cylinder will not miss for a while, then it will only do it when it's cold and eventually consistantly enough to set the check engine light on again.

I am thinking about chasing the threads, but is there anyway to check the tapper the plug should be sealing against. Also, what is the principle the plug seals on, is it the seat or the threads?

Any help would be appreciated.

Thanks