Ok my car is a little different, it's a euro 280 SEL. The car runs fine just a little rich. High on the CO and on the HC. I've looked on the posts here and went to check Pin #3 and there was nothing in pin #3, the slot is vacant.
Can anyone give me some input?

I have a pic of the sensors on the right side of the head, can anyone give me a clue as to what they are?

A little more info: I did feel a change in the perfromance recently as was opening it up to let out the cob webs and when I opened it up it had a serge of power like the throttle actually really opened up. As if the secondary's opened suddenly. The idle switch also shows a wide open throttle switch. I guess it's possible for it to stick. What do ya think?

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)

No electronic control, no O2 sensor. You will have to adjust mixture the old fashioned way. Measure it.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

There is an O2 sensor it's on the exhaust pipe. I just checked the closed throttle switch and it's good. There is no wide open throttle (WOT) switch like my book shows. I'm looking at an MBZ wiring book for a 1980 or so 280 SE. Mine is a 1984 280 SEL Euro. I wish I could read German. Even the fuse panel is in German!!! Still glad I don't own a Ford

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1984 280SEL, 62,000 miles
Euro model in the USA
1983 300D (Totaled out 10/2004)
New Factory Mint Green paint
Palomino int
1982 240D (Steak dinner for two)