Idle speed control valve
 

This was under the FE updates and I didn't want to get to off topic for that thread. What is the purpose of the idle control valve? Is it sole function just for drivability issues or does it have something to do with emissions?

My engine usually takes 2.0 mile to reach operational temperature this time of year. At the 1.4 mile mark, which is a stop sign, I've increased my trip FE by 2.0 MPG at that point which stays the rest of the trip. It's almost as big a difference as with and without EBH. I've had no driveabilty issue at all except for the first 15 seconds you have to feather the gas to keep it from dieing after start in P. In D no problems at all. This comes out to around a 10% increase.

The biggest reason I can see for having it is the driveability issues. I haven't had any problems except for the ones mentioned above about starting cold. The valve, I think, is mainly to keep the engine running fast enough to keep the battery charged when things like headlights, A/C, etc. were running.

On my car the idle speed control valve is used to hold a steady idle so idle speed doesn't change as conditions change or as the motor and various sensors get older. It's also used to raise the idle speed when the engine is cold, raise idle when the car is moving so using the power brakes and power steering don't stall the engine, and to raise idle when A/C is used. In a nutshell it's all about driveability.

My car will not run with the wire disconected, It will run if I keep pushing on the throttle but soon as I let up the engine dies.

My EGO sensor comes on line a lot quicker with a little more RPM so I think it is partly emission related.

I'm guessing you have a solenoid instead of a motor. The motor type remembers it's position when it was disconnected, the solenoid tupe is pulsed and spring loaded in (in your case) the closed position.

skewbe -

I checked for the Saturn, and it is listed in the manual under solenoids.

CarloSW2

an IAC controls the Idle basicly. Its functions are slightly different in some cars. Some have a AC idle boost thats seperate. The computer wants the engine to idle at a programmed speed, It adjusts the IAC as needed.

In the carburator days it was just the throttle minimum screw, that kept the throttle open enough for it to idle (When cold the choke opens it more)

typo, impirical evidence and physical examinations shared here all point to it being a motor, and a rather goofy one at that.

What is an EGO sensor?