I recently purchased an '82 300TDT w/ 268k. It didn't cost much, but it looks like it's about to. I missed all this in a short test drive, but since I bought it, I noticed that after I drive it about 15 minutes, it will shake badly at stops. I told this to my mechanic, whom I feel some loyalty to, and he said it was a common problem, nothing to worry about. He said it was a bad cylinder in the fuel injector pump which starts causing trouble after the car warms up, and that at $1000 part+labor, it wasn't worth fixing on my car. So I didn't worry at first, but now the shaking has begun starting sooner, and it also shakes when I brake to stop or when the car naturally decelerates down to a stop. (brakes&rotors brand new so it's not that, but that's about what it feels like)It's gone from bad to worse in 2 weeks. My questions are: Should I have other things checked out? Am I right in thinking this problem is not going to go away but will get worse? Also, I have always wanted a wagon, it would be worth it to me to spend the money IF that's really the problem...am I crazy? Thanks in advance for all advice!!!

Try This first
 

http://www.redlineoil.com/redlineoil/dfcti.htm

Try this before you spend a $1000 bucks. One bottle per tankful. You can find it at the Parts Shop or your local Pep Boys. Also it might be the timing.

Lisa,

You bought a Benz wagon in the first place, which is good evidence that you are not crazy. These are good cars. If you have to fix something, that's just a cost of motoring.

I suggest that, at the minimum, you check your motor mounts, and maybe just go ahead and change them. My daughters car had a slight miss and it got to a terrible point of shaking. Two new motor mounts and you could hardly feel the weak cylinder.

My guess, without seeing the car to tell how bad it is, is that running some "miracle in a can" through the tank as the previous reply suggested, along with a set of motor mounts will make this problem tolerable.

Best of luck,

Is bad injector pump on 300TDT really "nothing to worry about"???
 

I doubt if the pump is bad.They usually otlast an engine.The suggestions to try some addatives is on the money.Every car that old that has not had the job done should have new motor mounts.an easy and inexpensive job.These cars are almost bullit proof.Do the easy things first if worst came to worst you can buy from someone like potomac a used pump,for not much money.michael

Engine dies
 

Try this.

A rod runs from the accelerator pedal to the intake manifold venturi. Connected to this rod is another rod which connects to the rear of the pump (pneumatic vacuum governor. Try to shorten this linkage (rod connected to governor) up to such point the the engine doesn't die upon decelleration. Or, unhook the rod opposite the governor, and pull it up a bit while accelerating and decellrating. If it cures the problem, shorten it as needed.

This rod is supposed to mechanically assist the governor to stay at idle and not die during sudden decelleration.

I hope this helps.

Guys, I think you're missing the most likely culprit.

Given that it's smooth when started cold and only shakes
once warmed up, it's likely the rack damper bolt on the
injection pump. A bad injection pump or bad motor mounts
would shake all the time, regardless of engine temperature.

The rack damper is located on the backside of the IP,
just below the shutoff valve. To adjust it, loosen the
locknut, then turn the main bolt inward. There's no
formal adjustment procedure - just turn it in until
the idle is sufficiently smooth. Too far, and the car
will tend to stall. You can't hurt anything by adjusting
the rack damper, so have at it.

The good news is this task requires all of 10 minutes.

The rack damper does occasionally go bad. If so, you
won't be able to tune out the idle vibration. Your dealer
can supply a new, upgraded rack damper. Price is about
$25.

My old '84 300D shook like crazy at traffic lights until
I learned this trick. One adjustment and it was smooth
as could be.

Rack stop
 

Bingo! Rack stop would be my first quess. Never overlook the simple stuff that is quick and easy to check. I remember installing alot of the plates so that the rack stop could be installed....

Wow! Thanks everyone for your replies. I was told that the motor mounts are fine on this car, so it's probably not that. But the rack dampener sounds like the direction to go in first, and I will. Plus some Redline sounds like a fine idea, as well. It may take a few days to get around to this but I'll be sure to post back and let you know how it turns out.

I am glad that the rack dampener was suggested, that is what I would assume is the problem. Do a search on Rack dampener, because you will find many posts about adjusting it properly.

The key is to back it out all the way, after loosening the outer locknut. Turn it in until it just touches the rack. With the car running, rev the engine with the stop lever, and listen for a dead spot at the end of acceleration. If you hear a dead spot, turn the adjusting bolt in 1/4 of a turn, rev it again, etc., etc.. You will know when it is adjusted correctly, because your engine will not die, or idle irregularly when you come to a stop. I fiddled with mine for several weeks until it was perfect. I kept the two different wrenches in the car, and every time I drove somewhere, I turned it a little further in until the idle was perfect. It is sometimes hard to do without driving it between adjustments.

Congratulations on your Wagon!