This is from Dr. Booth. Hopefully the following post of Dr. Booth's will help. I hope I'm following protocol here for cross posting from another web site. Apologies to anyone in advance.
"The '84 190D doesn't have an overvoltage relay. Idle problems of a properly tuned 601.921 engine are usually caused either by the idle being too low (should be ~750 when the engine is warm) or because the temperature activated vacuum control system isn't working as it should."
See 7.1-010 D locted here:
http://mb.braingears.com/201_DISK1/PDF/60006.pdf
Marshall
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Marshall Booth
"der Dieseling Doktor"
'87 300TD, '85 190D 2.0, '87 190D 2.5 turbo, '84 190D 2.2 (retired)
Kevin
1979 240D manual
1984 190D manual