450SL fast idle
 

Wanting to adjust the idle air screw to see if my fast idle will change but it is stuck & won't turn. Afraid to attempt to apply too much pressure. Don't want to break it. Should move either way, correct?

Do you have fast cold or hot idle? KJET or DJET injection?

Furthermore if the screw is bottomed out then someone has already tried to adjust the idle down and you'll need to look elsewhere to get it to spec.

I have the Kjet. The Screw appears to be half way in or all the way out. I soaked it with liquid wrench but still wont turn. Car has been sitting for many years by previous owner.
Thanks

Yes that nylon screw can be hella tight. Normally they are mangled as well. I would remove the whole idle control unit and soak overnight in some carb cleaner. Then put in vice and use a long screwdriver for max torque and try and put all your weight on it so hopefully you don’t strip the head.