W126 idle air valve - test
 

I am trying to fix a hard start/rough cold idle problem and from a search it appears one of the culprits could be a stuck idle air valve.

Is is a valid test of the system (and to test the idle air valve) to disconnect the idle air valve electrically and look for a noticeable increase in idle speed to 1500-2000 rpm???

I have done this and NOT noted the increase in idle speed and now am wondering if that is my problem.

Thanks.This is a 86 560SEL.

Curious myself. Went to SEARCH and keyed in:

*idle valve*

22 hits - some better than others. You'll need the CD-rom. It contains diagnostic methodology for this problem.