Hello.
The problem with low idle and stalling has to do with the TPS Sensor.
My car needed maintenance and a week after that the car has the idle problems. It was maintened at a Mercury/Lincoln dealer.
I have now a other Qualified mechanic and he has checked the whole car.
The last time i got new o2 sensors and a IAC and TPS.
Problems were still there. Alsoo no vacuum leak.
My mechanic said that someone has turned the screw for minimum air (throttle) down.
But now my question: what is the best way to get the throttle back to it's basic position? So the minimum airflow will be good and the TPS sends the right values to the computer.
Greetings Bernhard.

Make sure the throttle body is clean. Clean it even though it may have a sticker on the body underneath the hose ass to not clean it. What I do is disconnect the iac and make sure the base idle speed is set high enough that the engine won't die. Ideally you want the base idle speed about 50-100 rpm lower than what the computer wants to control it at. I bet if you disconnect the iac the car will die. If the tps has been replaced in the past I doubt it's giving you concerns now and the adjustment of the base idle screw will only have minimal effect on the tps values to the computer.

I want that idle screw back to the basic position.
If i disconnect the IAC how much RPM should the engine run?
500 RPM?

500rpm would be ok. You might also want to disconnect the battery for 15 minutes or so to allow the idle to relearn itself after adjusting the base idle screw. You may have a fast idle condition without having the computer do a relearn.