I found this info on this tech site- question regarding engine surge on a 1988 300sel. The ovp relay was replaced with an update one but problam still existed to some extent (usually when my wife drove it), so I continued my search of the threads on this site and found one referring to the idle control valve and it's location. I did what was recommended on the thread (locating-removing-cleaning with carb cleaner-and replacing)and the surge is gone. This is good but the idle is a bit low now - I can live with that. Thanx to all Nickt