ICV-what's it for? and can high idle hurt trans?

[gmercoleza]

1991 300E, typical intermittent high idle (~1,800 RPM). I performed quite a few searches over the last few weeks, and already ruled out my microswitch and throttle linkage. Based on observations from others, last night I finally disconnected the Idle Control Valve while the car was idling high. Immediately the idle dropped down to 650 RPM and was smooth as silk. I drove the car around town for a few minutes, and boy was it NICE! I decided to leave it unplugged and enjoy the idle the way it was meant to be.

After leaving the car parked for a couple hours, I went outside and started it. It could barely keep running. Though relatively smooth, idle was about 450 RPM, headlights and dash lights were very dim. Turning off the A/C didn't increase the idle, it just smoothed it out a little. I think if I put it in gear it would have died for sure. And the engine wasn't even what I would call "cold" - there was still some temp reading on the gauge.

I revved the engine a little and noticed the lights got brighter and idle got smoother. So I held the gas down for a few minutes, with the engine at about 1000 RPM, until the temperature gauge climbed considerably. Then I released the gas, and joy of joys - idle was once again at a silky smooth 650 RPM.

Here's my question: What does the ICV actually do? Does it just provide input to the ECU in order to create a fast idle until the vehicle warms up? I am thinking of cutting/interrupting the harness to the ICV valve and wiring a simple on/off toggle switch somewhere maybe under the dash or in the glove box. That way, I could activate the ICV when the car is cold, then deactivate it when it's no longer needed.

Does anyone have any thoughts or suggestions on this crazy idea? Has anyone tried it before? I'm guessing replacing the ICV is going to be a very expensive proposition, but I hate the thought of jimmy-rigging an otherwise perfectly functional vehicle.

Obviously, I could also just leave it the way it is, where it currently idles perfectly 33% of the time, idles way too high (~1,800 RPM) 33% of the time, and somewhere in between the other 33%. But I am concerned that I might be slamming my transmission into gear more than it was designed for. I currently take my foot off the brake right before the trans goes into gear whenever the idle is fast, in order to reduce stress on the trans. Can anyone comment on any potentially negative effects of occasionally putting the trans into gear at about 1,800 RPM? Also, when stopped at a light, am I heating up my torque convertor or causing some other form of damage to the trans itself? 1,800 RPM in N or P, about 1,000 RPM in gear.

I definitely know I am taking some life off the front brake pads...

Thanks in advance!