rough idle and misfire

2004 MITSUBISHI ENDEAVOR
175,000 MILES • 3.8L • 6 CYL • AWD • AUTOMATIC
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JASON POND
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when my car warms up it has a rough idle and misfire. check engine light does not come on. the misfire is worse when A/C is on. I can drive to work witch is about four miles car runs fine by the time I pull in the parking lot it has a rough idle and misfires. I have changed the plugs and check for vacuum leaks. please help, thanks.
Aug 24, 2017 at 9:10 PM
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STRAILER
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It sounds like you have low compression in one or more cylinders. Lets start with a compression test.

Here is a guide that will help you get the job done:

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

If you do not have a gauge you can rent one for free from the local auto parts store.

Please let us know what you find.

Cheers, Ken
Aug 25, 2017 at 1:14 PM