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Q: Carbon fouled #3 and computer shows misfire on #3

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My car had a carbon fouled #3 plug and the computer showed a misfire on #3. I replaced the injector and plugs which solved the misfire and then there wasn’t anything showing on the computer. I began to get a lot of fumes from the exhaust and some light white smoke. In the tail pipe, there is some moisture. I had already performed a chemical test for a blown head gasket and that came back good. The fumes from the exhaust are getting inside the car when I’m driving on the interstate, especially if I’m passing a semi-truck. When I get the exhaust looked at, should they look for leaks or could the problem be something more than that?

A: If the car is running fine then it will mor...

If the car is running fine then it will more than likely have an exhaust leak. If the engine is starting to run a little rough again then it may have a valve issue in that cylinder. I would usually do a compression test just to make sure that the engine is fine internally. If it is, then the exhaust needs to be fully inspected because that is the most likely issue.

If you feel like you need assistance with this, contact a certified mechanic who can diagnose your exhaust system and make any repairs that are necessary.

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