Is this a new or old one? I believe the rack stabilizer is there to take out a little extra shake on an engine that is with in specs. It may not compensate for some out of spec issue.

To adjust it you should back it out so it has no effect on the idle rpm.

Adjust your idle speed with the Idle Adjustment Screw (not the rack stabilizer). How fast of an rpm range is on the emission sticker on mine it has 750 plus or minus 50 rpms so my max it supposed to be 800 rpm but an older engine may take a little more.

Notice that in general the idles is smoother at the higher end of the idle speed range.

Once the regular idle speed has been adjusted you turn in the rack stabilizer screw. What would be ideal is if you got rid of some shaking but did not change your idle speed.
You don't want the idle speed being adjusted with the rack stabilizer.

On mine I found that the new rack stabilizer had a much stronger spring and that the old one had part of the plunger worn off on the tip.

You decide if you want to do it with a Hot engine or cold engine. My shaking showed up after driving the car about 10 minutes and the engine was hot so I did the adjustment hot.

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84 300D, 82 Volvo 244Gl Diesel