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Q: My car randomly stalls

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car runs perfectly fine some days but some it days it will stall out at a stop light or when at idle. check engine light comes on right before the car stalls. do far i have put a new fuel pump, egr valve and curcuit, crank and cam shaft sensors, ngk spark plugs, and cleaned out the throttle body. after putting in each new part the car wouldnt stall for like 4 days then the stalling would occur again.

My car has 192000 miles.
My car has an automatic transmission.

This may be related to 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. This valve is controlled by the vehicle’s computer which 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. This is all controlled by the idle air control valve. 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. If you have access to an ohm meter, you can test the functionality of the valve by checking its electrical resistance. To do this, disconnect the IAC valve, connect an ohmmeter to pins 2 and 3 of the valve. If you get a resistance value between 10-14 ohms, it indicates IAC valve is working as it should. Next, connect the ohmmeter to pins 1 and 2. If you do not get a resistance value between 10-14 ohms, the IAC valve may need to be replaced. 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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