Q: My 2001 Mercury cougar will start just fine but will sputter/ shake then die when not pushing on the gas or stop/idle.

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This car has been very good to me being its older with how many miles. This is my first time driving it in the winter. It will start and everything turns on lights, heat and radio and I will let it run for a few because its cold 19-23° then it will shake vigorously and shut off as soon as I let off the gas. Which is so scarey to experience in the middle of winter traffic. I am out of state for work and have 2 days left and have to make the trip back home... It just started doing this today when I woke up to go to work I started it and it didn't really want to catch to turn on but weakly it did so I had no choice by to keep going. I put heet in my gas tank to help but I'm so afraid to drive it now...on the way to work when I would go below 30mph it would shake. When I would have to stop at red lights/stop signs/cars turning it would start to shake and want to shut off. I played it safe and tried to not come to a complete stop but a distance away so I could inch up. Please help!

My car has 150555 miles.
My car has an automatic transmission.

This may be a result 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. Since 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 making the transition from a higher RPM back down to idle speed. When the engine RPM drops below the normal range of about ~800 RPM, 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 replace your idle air control valve.

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