Q: Idle fluctuates and then stalls.

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I have 98 jeep grand Cherokee Laredo that has been acting crazy. it wasn't always do in it and now it's gotten so that I am afraid to drive it. While driving it hesitates and the rpms while jump but the motor doesn't. then while in park the motor would Rev on its own. eventually the battery light came on and it would die. battery and alternator tested fine. Now when driving it you can go a little ways and it acts as if it's not getting fuel you have to keep hitting the gas and it still sometimes will die. Someone mentioned a bad computer (pcm). something about my fuel pump not getting the right voltage? can someone please help!

My car has 235000 miles.
My car has an automatic transmission.

It sounds like you may have 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. 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 inspect your vehicle.

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