I have a 1982 380 SEC I had the same problem
1. Idle control valve is a silver thing about 5 inches long with 2 prongs on it. Mine is under the air cleaner when I changed that my idle went so high I also had to change the idle control relay a black box on my firewall. when I changed both of the the idle went back to normal.
2. mine also has an air/ fuel mixture the center of my air filter you turn it one way you get more air in the system if you turn it the other way you get more fuel in the system you need to find the balance of air and fuel so the car doesnt rock funny or want to take off when your at a light.
I dont know if your car has the same thing or not if you go to the benz dealer parts they can show you where the parts are for your car. when you find the parts check the hoses around it make sure they are connected and no holes in them.
hope this helps!
(benz with an attitude for parts but now getting much better just finished a new front end, brake system, fuel system, and new back sway bar bushings, new engine mounts, new engine shocks and much much more but finally getting so much better)