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Q: Truck's rpm fluctuates and shakes when idling, engline light on code reads: cylinder 8 misfire.

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The truck's rpm fluctuates when idling, the engine light code reads cylinder 8 misfire. I have replaced the spark plugs, wires, cylinder 8 coil, and cylinder 8 fuel injector but the truck still runs rough.

My car has 106000 miles.
My car has an automatic transmission.

A: If spark and fuel have been eliminated as t...

If spark and fuel have been eliminated as the cause, check for a vacuum leak. If there is one located near cylinder #8, it can be causing the misfire. If no vacuum leaks are detected, then a compression test is in order. There is a technical bulletin #PIP4138K from GM for this concern relating to a valve-train and/or camshaft issue. If you want to have this checked, a professional from YourMechanic can come to your car’s location to diagnose the rough idling to let you know what’s going on.

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