I was able to test the throttle switch today. Works the way the book specified - pins 1 & 2 have no resistance at idle, and 2 & 3 have none at full throttle. No connectivity at other positions.

What's next?

Would it work to test the idle control by giving the valve a steady 4.5V, and see if it smoothes the idle? If it does, it's the relay, if it doesn't, it's on to the the injectors and seals.

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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