Originally Posted by sixto

Put the MityVac directly on the shut-off actuator on the IP to see if the problem is the actuator or vacuum getting to the actuator.

You mean, pull out the vacuum line that goes in there and stick the tube of the mightyvac in there instead?

What oil are you using? If consumption is not an issue, try keeping the oil level between the upper and lower marks. [edit] I mean at the halfway point. Obvoiusly you'd keep it between the marks

Literally just got the car (a week ago). According to the previous owner, the last oil change is about 4000 miles back and he hasn't added any oil since then (and I think he is honest, I trust him). It was still above max. so I think it's safe to assume that the consumption is not an issue.

I don't think oil level has anything to do with the smoke. Read up on fuel cleaners and additives. Lots of good things written about Lubromoly Diesel Purge.

This MB mechanic I talked to about it told me that when it's been overfilled (apparently easy to do with this model), the valves can't function properly and will get noisy, and there might also be smoke as a consequence. When I pumped out the quart a couple days ago, when I started it up afterward, there were splatters of black oil coming out of the tail pipe at first (not before the pumping off of the extra quart, though....) The valves are noticeably quieter now....

Sixto
93 300SD 3.0