My mercedes shakes when it idles

When my 1982 mercedes 240d is in park, or when I am am at a stop sign, it shakes but once I start moving, the shaking stops. Any suggestions on how to fix this? Thanks.

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Body and Interior Specific Aid

Chassis Model Number

W123

shakes at idle

I read somewhere that the fuel injection pump "rack bolt" can be replaced with a Bosche upgrade and sometimes is the cause. I have also read that motor mounts and motor shock absorbers commonly fail. I'm not a mechanic so this could all be wrong. However, my 84 300D has the same thing right now, so I'm curious to follow this issue myself.

Reasons for shake at idle

There are quite a number of things that could be causing your engine to shake at idle. Many of them are covered in my manual "Diesel Performance Tuning and Repair." You will need to do a little diagnostic work on your own to find the reason(s). And yes, they could be multiple!

Here is a quick list:

Adjust your valves
Do a compression test (if cylinders vary more than 10 percent you may never get rid of the shake)
Check camshaft timing (timing chain stretch)
Check condition of your fuel injectors (this is a big reason if your compression is good)
Replace worn or collapsed motor mounts
Adjust idle speed.

Sorry but the 240D engine does not have a rack damper bolt. That is only available on the 5 cylinder turbo diesels.

Please post back the solution to your problem. I know others would like to hear. Thanks, Kent

Try this first...

It may be a slightly dirty or sticky injector. You can mix a little (half quart) Marvel Mystery in with your next fuel fill up. Pour a little in, add 5 gallons of diesel, a little more, 5 more gallons...etc. Mixing in Automatic Transmission Fluid in the fuel in the same manor will also work. It seems to lube the injectors, perhaps it burns off a little soot off the injectors. With a high compression engine, any imperfection in the injection makes a bit of a shake. It seems to work in my car. They seem to run ruff at times, and this seems to help. Also, get some 'Diesel Purge' and follow the instructions. That can't hurt either. If this doesn't work, your can check the stuff Kent suggests. A valve adjustment is always a good thing to check on...~Levon~

Same shaky problem in an '84 300CD

This shake is driving me crazy. Passengers get that, "what kind of jalopy is this?" look in their eyes, especially my wife. I first noticed it right after a new vacuum pump install, but I think it's just a coincidence. A local mechanic suggested it might be a warped valve. He adjusted the idle a tiny amount, which seems to have helped. In fact he said he has the same problem in his own W126 diesel and just lives with it to avoid the trouble of fixing it. I'm going to try the things Kent listed and see what happens.