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Idle problems 1997 Chevy 1500 Express Van

My fuel pump went out, the dealer replaced the fuel pump, but the idle goes crazy at times. When you are at a complete stop the idle is normal, when you acclerate the idle boast up and stays up while driving, until you come to a complete stop again.

No codes are set in the computer.

I replaced all vaccum hoses and P.C.V. Valve. It happens more when you get below half of a tank of fuel.

Sometime it acts completely normal for a few days and then returns.

any suggestions would be helpful.

Sounds like there’s a problem with the Idle Air Control circuit.

On the throttle body there’s a device called the Idle Air Control motor. This allows air into the engine anytime the accelerator is released so the engine can idle. If this device is failing to prevent air from entering the engine when the accelerator is depressed, this allows too much air into the engine. The O2 sensor detects this extra air and the computer adjusts the fuel mixture to compensate for this extra air. This then cause the engine speed to be too high for the throttle position.

The IAC motor may be stuck. So you could remove it and try cleaning it with a throttle body cleaner to see if this fixes the problem. If not, then the IAC motor could be defective and would require replacement.



Thanks for the info, I will check it out.