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Q: #3 Misfire engine light

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My Hummer is running fine, but the service engine light comes on and then off. The service engine code appears showing #3 Misfire. I have brought my car to several dealerships and the mechanics state there is only the #3 misfire. Is this possibly an electrical problem?

A: Yes, it can be an electrical issue. A misfi...

Yes, it can be an electrical issue. A misfire at a particular cylinder can be caused by ignition, fuel injection, mechanical issue, or vacuum leak. I’m curious why none of the dealership techs repaired it. Faulty sparks plugs, coils, or electrical connections can all cause this. So can a fuel injector or vacuum leak close to #3 cylinder. A leaking head gasket at #3 would also cause a misfire. Have a certified technician from YourMechanic inspect the misfiring issue and determine what fixes are needed.

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