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Q: Rough idle at 500 rpms

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Replaced #7 coil and spark plug after plugging in computer. Did not fix. Engine runs smooth while driving. 105,000 miles

My car has 105000 miles.
My car has an automatic transmission.

A: The first thing to do is a cylinder balance...

The first thing to do is a cylinder balance test to see if all cylinders pass this test and relative compression test. If a cylinder fails either test, then follow the pinpoint test and see if the injector is getting signal using a noid light. Check the injector for proper resistance. Swap the #7 injector with another cylinder injector or with a known good one and see if this fixes the problem. If you swapped to another cylinder, then the code will move from #7 to the cylinder you swapped the injector with. Replace the injector and clean all injectors using a pressure type injector cleaner. If you want to have this inspected in person, a technician from YourMechanic can come to your home or office to diagnose your car’s rough idling issue.

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