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Q: RPMs rise 1100 to 700; then to 1200; then down

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Recently the RPMs have been going from 1100 to 700 at idle; then up to about 1200 and then down again. After that there is a rough idle, usually followed by a loss of power if I am accelerating. My car begins to shake, drive roughly, and feels as if it wants to stall. I have replaced the spark plugs, PCV valve, and the air filter. I am wanting to replaced the IAC valve, but I can not find it. Can you tell me where to locate it and give me any advice on solving my car’s problems. Thank you.

A: Hi there. This is usually either caused by ...

Hi there. This is usually either caused by a bad idle control valve or a vacuum leak. The idle control valve is located near the throttle body. It can also be a dirty throttle body. I usually start by cleaning the throttle body and checking the intake for leaks. The intake manifold gasket is also a common failure. If there is no leak or if the throttle body is not the problem then the idle control valve should be replaced. If you are going to have this fixed, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the rough idling problem and other issues that are occurring.

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