Q: Rough idle and shakes at stops

asked by on March 09, 2017

When I turn on my car it feels normal, but after 5 seconds then I feel the shaking from what seems to be the front of the car as if it wants to turn off. The service engine soon light is on. Almost every time I am at a stop sign or red light it starts shaking a bit and sometimes very roughly. Usually starts shaking when warming up car. I am having no trouble at higher speeds. ONLY shakes when going very slow or stopped.

My car has 150000 miles.
My car has an automatic transmission.

What you are describing sounds like a dirty or failing idle air control valve. The idle air control valve monitors 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 and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. 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 while adjusting the air/fuel ratio constantly to allow this to happen smoothly. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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