I have a 1995 S350 that I bought 8 months ago. it had 108,000 miles when I bought it and now have 140,000.
Recently it has started to idle very rough once the engine warms up. At highway speed, seems to run very good, no loss of power and runs very smooth. My local mechanic, not a Mercedes certifed merchanic, but knows his way around the car, has checked the compression on the cyls and say they are all the same. He has narrowed the problem down to #5 cyl. He has switched the injectors in 5 and 6 and still 5 is the rough idle one. He is thinking it may the injector pump. But he does not have the equipment to test.
Has anyone else had this problem or do you have any suggestions of where we should go from here?
I also have the "door closing assit" problem. I can pull out the #9 fuse in the back and put back in and the doors and trunk work for about 3 closes then stop again. Is there a good source of rebuilt or used pumps for that.
I enjoy reading post at this site and thank you for your help

1995 S350
1992 300SE

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Run a search on this site for delivery valve seals and o-rings (on the injection pump). More than likely, thats the source of your #5 cyl rough idle.

While you're at it, run a search on "rodbender".

Mine does this on start up or when it is idling once in awhile. It will shake the whole car until I bring the rpms up past 1k or so. It doesn't sound like it is skipping but feels like it, if that makes sense.

I have been told that it is the governer in the IP dieing. A rebuilt IP is about $600 not to bad I plan on doing mine eventually.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

i chased a rough idle on my 90 350 for a couple of months. found injector seals missing (the little metal button looking things at the bottom of the injectors). helped but eventually found that the fron t three injectors were working loose. locktited them and now it purrs like a kitten. this sounds as if it is not your problem,... yours misses right away not after driving a couple of days, right?

at 140,000 i would not suspect the injection pump. i am thinking it is something stupid, simple and hard to decifer like mine was.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

read this idle problem 1998 e300 td please help it may be the same problem, Joe