This one sounds more like a linkage problem.

Follow the throttle linkage up to the front of the engine to the bellcrank from which there is a rod that goes down to the throttle plate. Pop the rod off the bellcrank to be sure that the throttle plate can fully close. Start the engine and see if the idle drops.

If it does, work your way back through the linkage to see where it's hanging up.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe