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Q: My car had a rough idle, and if I sit at a red light or let the car run in idle for a few minutes my check engine light starts to

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My car has a rough idle, and constant flashing CEL and service stabilitrak, and traction control light comes on, I had the code ran and it comes back as a misfire on cylinder 4, I was recommended by the auto zone clerk to change coil and plug. Plug was fouled, replaced coil and plug. No change.Any ideas of what it could be?

My car has 153000 miles.
My car has an automatic transmission.

A: A dead misfire on a single cylinder may be ...

A dead misfire on a single cylinder may be deeper than just a spark plug. If the compression for that cylinder is very low, the cylinder cannot fire. Low compression would be caused by worn piston rings. Also, if the fuel injector is leaking or not flowing enough fuel, this may cause a misfire as well if the injector is leaking bad enough. A fouled spark plug usually leads to a coil that is not functioning or lack of compression in that cylinder. If you would like to have this taken care of, a qualified professional from YourMechanic can come to your car's location to diagnose the rough idle and help you move forward with repairs.

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