My 91 GMC Van has an Idle Control Valve that is unplugged, but the van still runs great. Will the valve being unplugged, result in harm to my vehicle?
Your van runs good because the computer has learned the driving style, if your battery goes dead and the computer resets, itd be about 200miles before it relearns the vacuum tolerance , and because the idle air control valve is disconnected it must of been when the solenoid was in the right spot. Because the idle air control valve is disconnected, your gas milage will suffer and your computer wont be functioning right, not being able to compensate form different road conditions/weather/wide open throttle.
As long as the eng check light isn't on then it will harm nothing. If the light is on but the van runs good it's because the computer is running in a fixed parameters ( emergency mode ) and it's not running at top potential.
Go to your local library, ask if they can get you the *factory* GM wiring diagram and service manual for your specific year/vehicle. They have a troubleshooting section that is usually quite good, with easy to follow flow charts. IAC is tied into the ECM in the way it handles air when you aren't using the gas...decelerating, stopping, when you start the vehicle (and different depending on whether the engine is cold/hot), etc. It will be stuck in one position now. When it starts to cause problems, you'll see them manifest in the conditions I describe above. If there truly no issues with the way it runs, then don't worry about it until you start to have problems. It's not going to destroy the motor without it. Not my cup of tea to know there is a problem, and ignore it, but then again, I'm me. You can rest assured though, if it were unnecessary, and saved GM one penny to not give it to you, they would not have installed it in the first place. :)
