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Q: Car shuts off on idle

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Hi,

I've invested quite a bit in replacing parts on this vehicle and out of the handful of problems I'm left with one that has been there for about 3 months. Normally at idle, or below 1.2k RPM the car will shut off. About 1 out of every 80 idles, but it's starting to happen multiple times per day now. Sometimes it will start on its own immediately after but sometimes it requires a jump. After a jump the car feels revitalized with handling and driving; it's odd. I've tested the battery voltages and with AC on full, lights on, accessories on and engine fans on the battery is still testing at 13.04V - 14.75V so I believe the alternator is working. At rest, ignition off, the battery is constantly between 12.6V-12.8V. I'm not getting an engine code from the computer. I've checked the drive belts and replaced them all are functioning properly now. I'm left with fuel delivery or idle engine processes... Help! :-) Please and thank you.

My car has 164000 miles.
My car has an automatic transmission.

A: This is a common sign of a dirty or failing...

This is a common sign of a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. As this valve is controlled by the vehicle's computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and repair your idle air control valve.

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