Idle speed solenoid, 280SL A/T

[TheEngineer]

I find that the ISS (the round thingy on top of the intake manifold with 2 wires) sticks in the extended position. It operates when the selector for the A/T is put in gear (any gear) and extends 5mm, thereby pushing on the throttle linkage. This increases the engine speed which otherwise would decrease because of the drag of the engagement of the A/T. When it sticks in the extended position the idle speed goes to 1000 rpm when the gear shift selector is shifted to neutral or park. I found that the iron slug inside of the solenoid retains some magnetism and sticks because of this magnetic attraction to the forward stop. It takes often more force to return it than what is available from the return springs, a little engine shake helps. It is not satisfactory. I am thinking of taking it apart and installing a forward stop of a non magnetic material. Any Ideas? 

[vande17941]

Replace it. They have almost zero resistance once the voltage is cut.

[Cees Klumper]

I think the 'taking apart' bit is what has stopped most so far. Requires drilling out but I see no reason why they couldn't be rebuilt. I have my old one sitting on the shelf for a future repair attempt (altough mine had become 'lazy' rather than you over-active one).

[TheEngineer]

Allo Cees Mon cher ami!

[Tyler S]

Try reversing the polarity of the 2 wires. May be enough to change the magnetic memory the slug has retained.

[TheEngineer]

Attached see pic of disassembled solenoid. There is a brass washer for a stop and I replaced it with a thicker one. Works fine now - no stickum. Current draw before modification 1.02 amp, after installing thicker washer 1.03 amp