After reading several posts about the subject, I felt confident enough to try to repair the fast idle problem on our newly purchased 84 grey 500sel. That was a mistake. It appeared to be set at cold idle speed. After replacing the oil temp and water temp switches, no change still idles about 900-1000 rpm always. After checking ma to valve, removed valve, cleaned valve, no change. Car has abs and ovp relay seems intact. Car does not have lambda control or O2 sensor. Throttle switch has only 2 wires that open off idle. Terminal #7 on controller at 12 volts at idle changes to floating mvolts off idle. Jumper term.1-2 and4-5 idle control valve shuts. Now idle controller does nothing (no ma output). Checked fuses, ovp, replaced controller no change. The control valve operates when 1-2 and 4-5 jumpered. I have been unsuccessful in the last month to get any service manuals other than a chiltons. Mercedes USA recalled 126 cds. I'm out of ideas and am currently using a plumbing washer to keep idle down to 1100 rpm. Frustrated, but what am I missing?