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

I'm tempted to say that it needs a new delivery valve seals but the usual symptom is nailing - a very painful sound like hammering a chisel into concrete.

Sixto
95 S420
87 300SDL