If the other suggested stuff does not work listen with a piece of broom stick or a mechanics stethoscope to see if you can locate where the noise is coming from.

The Vacuum Pump having issues can make noise.

Removing the small steel oil pan and looking in the bottom for metal fragments might also tell you if something is destroyed.

When I first got my Car the engine would shake and the Air Filter Housing would pound on the intake manifold. Some where there is thread that tells you to put a piece of 3/4" or 1" heater hose between the manifold and Air Filter Housing.
The noise was bad and sounded like something was going to break off.

The same as above but caused by a broken Air Filter Bracket.

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84 300D, 82 Volvo 244Gl Diesel