I have read the gadget is really a motor driven valve, that rotates and when some ports pass each other, the air actually flows, and when they are not lined up it does not flow any air. The speed of rotation controls the airflow and thereby the speed of the engine. I am not entirely sure about all this but the "idle motor" as it is called, should be something you can do a search on and get some additional info on.
I have read here that if you take it out and try to turn the inner drum or whatever it is with your finger, or something you can push against the drum with through the port, you can free it up. Cleaning after that is done by partially filling it with a solvent/cleaner or gas, and vigorously shaking it, then draining. After a few times it should get easier to turn. I am not sure if you should not spray some lubricant in there when you are done or not. But the idea is crud builds up in there and impedes the ability of the motor to control speed, or make it rotate at all.
You can check it by wiring it back up and turning the ignition on and it should start rotating.
That is about all I can remember reading off the top of my head. I am sure if you do a search you will find some of the threads I read and get more detailed and specific information. I think these "idle motors" were used on quite a few models.
Good Luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)