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Q: Engine idle fluctuates and dies.

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When I come to stop at a red light my rpm doesn't go lower than 1 and when this happens ( which is always) it gives me a big kick then stalls. Also when I start it up in the morning the rpm goes straight to 3 and stays there until I put it in drive. Then when I do this it doesn't by go lower than 1rpm . Why are these things happening???

My car has 200503 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 and eventually stall. In the mornings it is normal for the engine idle to be a bit higher than normal when you start the car as this is the cold start enrichment process which allows the engine to warm up sufficiently, however this should cause the RPM’s to hover around 1,200-1,500 or so, not 3,000.

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. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

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