broken idle adjustment knob

I just turned my idle speed adjustment knob to the left before cold starting my '79 300SD. The tension "gave", I heard a slight clunk, and the knob just spins now. Anyone ever have this happen? What part do you suppose broke, and how difficult is it to replace?

[Ted2222]

Patsy,
Not certain that our cars are the same, but on my 240D there is a metal piece on the end of the cable (under the hood). The cable goes into it and is held on by a set screw. Mine came off once and I was fortunate to find it still lying on the engine later. You need to find yours if it is still there or acquire a new one and install it.

The clue on these is to hold the accelerator down while turning the adjustment counter clockwise. This relieves the tension on the cable because it is not trying to pull all the linkage and the injection pump adjustment along with it when you turn the adjusting tab.

Hope this helps. Good luck.

Thanks Ted, I looked at the cable and that is all intact. I think that tomorrow I will take out the instrument cluster and look right behind the black plastic dial. I think that the cable broke off behind the dial if that is possible. I read that our '79's were the last year to have this idle adjustment control.

[Ted2222]

Upon rereading your original post, I suppose the freely spinning knob should have been the clue.....sorry about that.

If you car is configured like mine (again!) you may find it only necessary to remove the panel over the driver's legs to get to the cable and not have to remove the instrument cluster. Don't know enough about your car to be sure.

In any event, hope you get it solved easily.

Ted, I got lucky(thanks to Mercedes design). I just repaired my knob! I took out the gauge cluster( I do it often so it is never really in there- I can pull it out while driving !) I also took off the lower panels( Hey! I have a C.B. radio). The small pot metal box with the end of the wire, and the cams that move in and out, had the top pop off. I was able to locate the top( and a small screwdriver lost previously), hiding up in all the wires. I regreased everything and pinched the top back on with pliers. I am so glad it was repairable. Any other car would have needed a new cable, I'm sure! Thanks for the input