Odd W126 Idle Control Valve with a speed adjusting screw

[bolomiester]

Over the weekend I was digging through a box of parts I bought at a swap meet, and found an idle control valve with an adjusting screw in the top. I was surprised as I thought these things were not adjustable.

Anyway, I soaked the inside with brake cleaner over night, then with WD-40 for half a day, then more brake cleaner to flush out the WD-40.

After I installed the valve I discovered that turning the screw clockwise reduced the idle speed and turning it counter clockwise increased it.

I experimented a bit and discovered that having the screw turned about 1/2 turn out from all the way in made the car idle at a perfect 650 rpms in gear or out of gear. Something it has only done for short periods before. It will be interesting to see if keeps it up or goes back to its old trick of idling perfect in gear, but jumping up to 1000-1500 out of gear.

Has anyone ever heard of a W126 ICV with a speed adjusting screw before? Is it possible that it's from some other kind of car?