Idle mixture needs adjusting, the O2 sensor is probably shot, and the temp sensor may also be wacked.

If the meter reading is off, mostly likely the O2 sensor is bad, but it could also be a disconnected wire (hehe) or a short.

There is a nice section on diagnosis, I think here on MErcedes shop, in the DIY section (I may have seen it somewhere else, though, getting a bit foggy upstairs....)

Make sure everything is in working order before setting the idle mixture.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!