Thanks for the replies. I have not been able to look at my 240D till yesterday. I took the nut off the the idle speed control at the dash, turned it with pliers and noted it did not move the throttle lever. I then noted that the cable close to the knob was kinked into an S shape. I bent it back straight and now it seems to be working ok. Increasing the idle to 800 - 850 rpm makes for a smoother idle.
At 700 rpm, the idle is noticeably rougher. I wonder if the rougher idle has to do with the uneven compression numbers (I'll post them later). I still have to check the valve adjustment but they should be ok per the maintenance logs of the po which indicated they were done less than 2K miles ago.

Who carries the idle speed plastic knob other than the dealer?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked