I have been waiting for a service CD as well. I had one for my 124 and it saved me dozens of times. Although you will find this board to great too.
As for your problem, this is a shot in the dark as I have not yet needed to address this one myself... but you may consider inspecting the throttle linkages. They may be loose.
Has this only begun recently? You may have just picked up a bad tank of diesel and/or have some water in the system. From your signiture I do not know where you live, winter?, or how many miles is on your car.
Have any dash lights or messages been tripped?
1996 (W210) E300D 86K - Traded in for a Lexus
1992 (W124) 300D 2.5 Turbo 202K - Sold
1983 (W123) 300D, 146K - Sold
1970 280S, 263K - Sold - Beginning of addiction