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Q: Rough idling

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My car has about 60,000 miles on it. When I'm idling at a stop sign or red light, or if I turn on the A/C or fan blower while I'm parked, the car will shake a bit. It sounds like it's struggling for power. Previously, I would drive the car about 35-40 miles to work every day, though now I only have to drive two miles. Could there be some build-up in the engine that it needs to "burn off", or do I need a gasoline treatment of some kind? New plugs? What else could cause rough idling in a car that's still fairly new?

Hi there. Most of the time, this is caused by a dirty throttle body. If there is build up in the throttle body bore, then the throttle plate will have trouble racing the correct location keeping the engine from maintaining the correct speed when an extra load is on it like when the A/C is on.

Also, being that you now drive a short distance, the engine may not have time to fully warm up which can keep the idle from reading the correct speed, and the lack of temperature can cause carbon build up in the engine. I would start by cleaning the injectors and the intake with carbon cleaner and cleaning out the throttle body. That should take care of it. If you need to have this done, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your rough idling issue and perform any of these services as necessary.

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