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Q: Rough idling after sitting for a few days

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My car has gone 60,000 miles and it has been idling rough. I had the spark plugs replaced recently but it didn't fix the problem. This usually happens when the car sat for a few days. What is causing this? I should mention that I fill it with high-quality gas.

A: Hello. If the ignition coils are misfiring,...

Hello. If the ignition coils are misfiring, this could cause the spark plugs to misfire and the car may idle rough. If this is the case, the ignition coils will need to be replaced in addition to the spark plugs that you replaced recently. It is possible that there is a high carbon buildup in the throttle body and intake, causing a rough idle condition. In addition, there are several sensors in your engine that have been known to cause this same problem. Have a certified technician, like one from YourMechanic, complete an inspection of your vehicle to determine why your car idle is rough.

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