The check is to find the idle air valve, which is a silver cigar-shaped gizmo on right at the center front of the intake manifold. It has a two pin connector on the front. Pull the connector about halfway off and with engine idling, measure the voltage at the pins - one test lead on each pin. If the idle relay is working, you should see 3-5 volts.

Various online suppliers sell units rebuilt by a company called ProgRama.

If you have voltage, the unhook the connector and touch battery voltage to the pins. If you don't hear a soft click, then the valve is bad.

If the valve clicks, then take the valve off, plug one of the air passages, and fill it up with carb cleaner, shake it up, and let it sit for an hour or so. Dump out the cleaner, and repeat until no more crud comes out.

Reinstall the valve and maybe it will work.

__________________
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