My 88 420sel starts fine and idles cold about 1000-1050rpm, but seems to have a slight miss at idle only. It also warms up and seems to stay at around 850 until I put it in gear and it bumps it back up so idle remains at 800 in gear, which makes it pound into gear a little hard. The engine runs strong and smooth on the road whether under a load or not, and shifts firm and positive, but when you come to a stop and pull the car out of gear it comes up to the 1050-1100rpm range. This is the first mercedes I've owned and do not want to continue driving this like this, it seems awful hard on the drive train on the initial shift in either d or r and the miss at an idle is both annoying and embarrassing. The car has 118000 miles on it, and I just drove it back from N.J. about 420 miles and got 21.6 mpg and it drove great other than the problems listed above. Any help would be greatly appreciated. Thanks very much in advance. CB

Hi euromaine,
there is a lot of stuff on high idle in the posts, so a search will give you a lot to read. My 87 idles at about 500 in D and goes to about 750 when in N or P. So 1000 is too high. There is an idle control valve under the air filter housing that can be cleaned.
Good luck

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Thanks for the input RKreutzer! I'm going to replace all the vacuum lines and check to make sure the linkage is returning completely, and clean that vacuum valve that you were kind enough to point out. I've spent alot of time working on other brands of cars and trucks but I am very unfamiliar with the Mercedes way. This is my first one and it has a few small issues but for the most part is very nice. Thanks! C.B