ist located under the air cleaner....take it off and should be to the front of the engine......heres a picture of it..

http://catalog.eautopartscatalog.com/mercedesshop/sophio/image.jsp?title=Idle%20Control%20Valve&url=http%3A//img.eautopartscatalog.com/live/C403024259BOS.JPG I cleaned mines by removing it and spraying it with carburator cleaner and then I oiled it with WD40.