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Q: Car jerking when slowing down

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My car sometimes jerks while I'm driving it feels like it's about to die on me. It mostly does it when I'm slowing down. I just got my spark plugs replaced thinking that would solve the problem. But it's still happening.
My car has an automatic transmission.

A: This is a common symptom of a dirty or fail...

This is a common symptom of a dirty or failing idle air control valve. As you know, 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 with the help of the idle air control valve. When the engine RPM drops below the normal range of about ~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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