I had a 1986 190E 2.3-16 with over 200k miles, that is now my son's. It is also a Euro model, and at about 60,000 miles the "idle motor" died and my car did a lot of the things you say yours does. I had the dealer change it out as I was intimidated by the task at the time. I have not had an idle speed problem since.
I have read here that you can clean these things and they go back in fine. I will try to clean this one if it acts up again. The original one was slightly smaller and a little different in the details of the shapes on each end.
I have been lucky so far as mine has needed relatively little other than regular maintenance which I have done myself. So, I am not familiar with a good CT mechanic with experience on these cars. If someone knows one, I would also be interested. Mine, make that my son's, needs some head work now and I would prefer to give it to a shop where this one is not the first such machine they see. Hope this helps, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)