The oscillation of the fuel rack at idle was a problem with those years Turbodiesels. The problem is greatly accentuated by too high of an idle speed. It seems that motor often has a higher idle after a hot run also.
The first check I would do is to pull over to a safe parking place and do a little diagnostic. With the engine idling (poorly) push lightly on the "STOP" linkage. This will drive the idle down. Drive it slowly down and see if the engine smooths out. It probably will.
If thats the case a proper idle set up is in order by someone who can read the actual rpm. There are a number of different types, the one we use is made by Snap-On. It clamps to the number one injector line and the battery. It makes a signal that a standaard timing light uses. With a light that gives rpm and light indication you are all set.
The first fix that MB had to the 116 body car was to add a rack dampener to the rear plate of the pump. A proper adjustment will include this adjustment also.
The next step is a compression test and injector bench test if the results are good. Next pump element brass seals and then send the pump out.
BTW if you use this timing method you have to use different specs than the drip or high pressure methods.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician