CIS--E-III Idle speed

[mboucher70 at hotmail.com]

Question regarding the idle speed on an Audi 100 with NF engine.  

I had read somewhere that there is no idle speed adjustment.  Its handled entirely by the ECU and Idle stabilizer.  When working correctly, once the idle switch goes closed circuit the ISV kicks in and regulates the idle.  Thus if the car occasionally stalls at idle, either the ISV is sticking, malfunctioning, or there's a vacuum leak.

At the same time, I've noticed that there is actually a screw on the throttle body for adjusting the idle speed.  Is this screw simply for the purpose of setting idle speed by bypassing the Idle stabilization system if the Idle stabilization isn't working right?  As I understand, when the screw is adjusted enough so that it actually sets the idle speed, the idle switch never goes closed circuit and thus the screw sets the idle speed, not the ISV?

If I don't use this screw, my car idles great when the weather's cold, but once its warm, and the car is warm, it will occasionally stall if for example I do a sudden stop.  Its almost as thought the ISV doesn't quite have time to do its thing.  Other times, it might just about stall with rpm dipping under 500 but then the isv kicks in and brings it up to around 700.

I can avoid the stall by setting the idle speed to around 700 when the car is warmed up.  But then it seems to be idling unnecessarily fast when its cold.