Q: Idle fluctuates

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It shutters and idles rough between 0 -500 rpm in idle. The Instrument panel flikkers and the radio turns on and off. What should I do?

My car has 169456 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a dirty or failing idle air control valve causing your engine idle to fluctuate. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. As this fluctuation in idle happens, this may also cause the charging of the alternator to fluctuate slightly as well resulting in the lights flickering or dimming slightly as the engine RPM drops. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

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