Unplugged the potentiometer and restarted. Idle went to 1500 again, but then bounced back and forth and settle on about 700 in park, 550 in drive. Runs rough with pot unplugged. So I am guessing an adjustemnt needs to be made to the position of the pot. What is the best way to do this? Car running? measure voltage from pins with the connection unplugged?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E