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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 15377
Experience:  Have owned a repair shop for 25 yrs.
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1994 Chevrolet: a 5.7L Throttle Body V8 and manual trans..RPM

Resolved Question:

I have a 1994 Chevrolet 3500 4X2 one ton dump with a 5.7L Throttle Body V8 and manual trans. Recently it has developed a problem of run-away idle. When I start it up the idle RPM's slowly increase until the motor is absolutely screaming. Drives OK but at a stop sign the motor will still race. Someone suggested I try replacing the Idle Air Control Valve (IACV) but this did not change anything. Thank you in advance for your help.
Submitted: 6 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 6 years ago.


you need to check for vacuum leaks.check the gasket under the throttle body..check to make sure the throttle isn't hanging up on anything and the tb butterflies are closed at an idle..but the problem may be the egr valve..remove and clean it,make sure it shuts off. or the egr valve solenoid[this is what the vacuum line form the egr connects to]this may be opening the egr valve when it don't need to causing a vacuum from the exhaust


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