91 W124 has a intermittent rough idle some times I can gentle quick spike the throttle and it will return to a smooth idle until the next time I come to a stop. initially this was most noticeable in gear stopped at idle now it seems to be more noticeable even in nuetral and now the throttle spike seldom smooths it out. the car has 195k on it. Unsure what may be causing this. To clarify the idle quality is not major shake like I have seen in an 84 603.
Last detail that may be related is. My power output is actually better than it usually is and I am having temp issues under load ( the temp issues have existed on and off for the last few years so am unsure it is related),

I had simillar problems with my 1987 300D .... I swapped out the worn motor mounts which smoothed out the engine tremendously and I replaced all the worn vacuum hoses in the engine compartment and the idle problem went away. I'm not sure which hose I replaced solved the problem but the hoses on the passenger side that were connected to the EGR, Turbo, and the vacuum controls by the airbox were in really poor shape and obviously leaking so I suspect those contributed to the problem. I suggest starting with getting a couple meters of vacuum hose and a few molded angled fittings and just start replacing lines one at a time. Some lines may look ok but they may just crumble or break when you try to remove them. Good Luck!

Thank you very much... sounds like the vacuum lines may be the cure... I was beginning to wonder about the injectors.. this is a much better solution... when I get it done I will report back with results.

best

Chris