To add to the image above -- just posted the below in your other thread, pasting here as well for future reference, although at the risk of redundancy.
Bottom line -- the idle speed screw you are asking about and that is referred to in the diagram above will adjust WARM idle (with the caveat mentioned below about the linkage rod from the throttle spool that may need to be changed also in order to get you full adjustment latitude on the screw). That warm idle adjustment can be made after the engine has reached full operating temperature and the cold start advance system has therefore fully backed itself off to the warm position.
COLD idle is set by the position of a ball stud on the top of the cold start advance arm (side of the injection pump), which contacts the throttle lever and kicks up the idle speed when that cold advance lever is being pulled on by the cold start thermostat. So you will need to move that ball stud back to reduce how much the CS arm pushes the throttle lever forward when cold.
Both warm idle and cold idle, with these two separate mechanisms, will need to be re-adjusted anytime the smoke screw position has changed.
NOTE! You want to adjust the BALL STUD POSITION ONLY on the cold start advance arm. Don't disassemble the end of the cable that moves the entire CS arm or try to adjust things by changing anything about that cable. If you do, then you change not just idle speed but also cold timing advance (which you don't want to affect), and then the cold start system (theoretically) needs to be re-set on a Bosch fuel pump calibration bench.
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once you have the smoke screw set to where you want it, you will need to make two other adjustments: one to the position of the low idle throttle lever stop screw (see photo and info ngoma posted), and additionally you will need to adjust the position of the ball stud on the cold start advance lever that kicks the throttle lever up to a fast idle position when the cold start advance system is in "cold" position. It will need to be loosened and adjusted towards the rear of the car. This will probably take a few days of cold starts to get where you want it, aiming for about 1000 rpm idle IIRC when cold and then 750-850 when warm.
Further -- and this part is specific ONLY to Volvo cars, unlike the steps above that apply to all engines using the Bosch VE IP -- you *may* also need to adjust the length of the turnbuckle style linkage rod that runs from the bottom of the throttle cable bell crank spool back to the actual throttle lever (and/or, adjust the position of the ball stud on the throttle lever that that rod attaches to). This is because, as you turn the low idle adjustment screw outward to reduce low idle speed setting, eventually you may reach a point where the throttle mechanism is no longer resting against that screw and instead being stopped by the throttle bell crank rotating to its minimum stop position. This is not desirable - you want the low idle screw, not the bell crank, to set low idle speed and you want an air gap clearance at warm idle between the bell crank and its stop. The factory greenbook gives a clearance spec for all this. It's due to Volvo's funky two-part progressive throttle control mechanism that they adapted to VW's engine, resulting in the additional fiddly adjustments, but it all works very nicely provided you get it dialed in.
May want to finish final adjustments to the smoke screw before undertaking all this. (aiming for just at the point of a slight puff of smoke as you push pedal to full load, and then it should clear up entirely once under steady full load, don't want any continuous black smoke) Since any further tinkering with that smoke screw will cause you to have to redo your adjustments to idle speed and related parts again.
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