350SD: Car shakes heavily at low idle once warmed up.

Hi, My wife has a 350SD (W126 - 1991) with 146k miles. We have had it only for the last 15k miles or so. The car has developed a strong throbbing, low frequency vibration or shaking (the whole car) when stopped at a stop light (for example) after it has been driven for a while and is well warmed up. It is slightly noticeable, but much less severe, when started up from cold. Otherwise, the engine seems to run smoothly and be OK at higher RPMs. I have noticed that the idle speed drops a little from, >6500 to

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Diesel Engine Specific Aid

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Chassis Model Number

W126

probably mounts

Hey Russel, I just had a similiar problem, replaced both motor mounts and now it is smooth. It was not expensive to do myself, but access was a bit more difficult that I expected. Mine would vary with temp, day to day, etc. but always smoothe out at higher rpms. I drove it so long like that I forgot what how smooth it used to be. Hope that helps, Steve

Steve, thanks for the input.

Steve, thanks for the input. Sounds like I need to get under the car and have a closer look. Russel DeLombard 1991 350SD 1981 240D Bainbridge Island WA 98110

Check the injector pump

I had the exact symptoms you describe. Car started and ran fine, but it looked like I had the palsy at a stoplight. Very annoying. The motor mounts were fine. The engine shock was new. I couldn't figure it out, and my regular diesel-owning Benz mechanic couldn't either. Finally took it to a former mechanic who figured it out... Inside the injection pump is a sliding plate that balances out the fuel from the injectors and, as I recall, makes sure it's smooth. This plate has a spring on it, and anyway mine was broken and worn out. Replaced it in about an hour and the shake is GONE. This country mechanic called the part a "shake-plate bolt" but I've never found that name online.