Fix all the cheap stuff that can cause the hot idle shaking

Adjust the Valve

Make sure there is no Air leaks, typcal sources the Oil Style Hand Primer, the 2 sections of inlet Hose and cracks in the Plastic Filter

The idles speed should be with in the normal limits

If you can take yours apart the Fuel Pressure Relief/Overflow Valve Spring gets compressd over time and the Service Manual has that you can stretch it back to 27mm of free length.

If it is shaking badly a new Rack Damper/Governor Idle Pin may or may not help.
At your Engine Milage is enough to have worn out 2 sets of Injector Nozzles. (The Valve adjustment and rebuilding the Injectors too away most of My hot idle shaking.)

If you change the Motor Mounts remember the Transmission Mount also supports the Engine and Transmission.

If you still have issues after the above stuff is fixed a Compression Test is in order because you would suspect uneven Engine Compression.

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84 300D, 82 Volvo 244Gl Diesel