I have a 1983 300SD (126 Chassis). The car has a serious vibration when in idle and and low speeds, the vibration is somewhat less at higher speeds but is still noticeable, also the engine does not shut off when the key is turned off and removed from the vehicle!! I have to choke it with a hard step on the accelerator and turn it off immediately at a high RPM. I believe that this is a vacuum leak (I may be wrong of course); if in fact this is symptomatic of a vacuum leak could someone with the expertise please point me to the right vacuum hose or hoses which should be checked. If I am wrong please give me your best suggestions on how to find the source of this problem and what steps to taken in order to fix it. Thank you. Haresh

I have an 82 300sd that had the almost exact same symptoms. Its deffinetley the vacuum system. My problem was fixed almost immediatley after i discovered a hose that was disconected right by the vacuum pump itself. Looking at the engine from the front, the vacuum pump is located to the right rear under the hood (right above the front left tire and right next to the main fuse box). Just follow all the lines from the pump and see if you can find any leaks or disconnected hoses. This of course is assuming your vacuum pump works. Anyone with better knowledge please correct me if I am wrong.