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Q: Service engine light flashes when accelerating and driving rough

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Started vehicle today and didn't turn over immediately which is odd. Started on 2nd try. When at a stoplight idling it "shook" a couple times. Was fine on highway until suddenly the service engine light started flashing and it began driving very rough when accelerating. Every time I accelerated the service engine light would flash. Did this the entire way back home. No issues when coasting. Rough idle when at stop lights. What would cause this? Has never happened before.

My car has 155000 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. 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. When the engine RPM drops below the normal range of 750-800 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 repair your idle air control valve.

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