idle control valve

My 1991 190e 2.3 has a fast idle. It idles around 1400 rpm. I recently got the car running thanks to the help of this forum. It had a broken wire in the td signal wire from the control module( THANKS JOE BLOGG). All of the electric connections are correct as well as the vaccum lines and timing. What I need to know is when the idle valve is closed is it supposed to be completely closed or partially open? If there are any other suggestions as to where to look to correct the problem I'd appreciate the input. Another thing , I adjusted the idle mixture inadvertantly and think I corrected it pretty close, but would like to test it to be sure. How would I go about this? At a cold start it takes a bit to get it started and keep it running until it warms up a bit. Thanks for any help.