A 190 had a "dumb" computer and will not store codes, and to get any info out of it you must have the MB tool that plugs into the diagnostics socket (round, with a screw-cap, on the left fender).

You are running over-rich, and will have to find out why. It could in fact be a defective cold start valve -- check it for drips with the engine off after a cold start. It "plugs" into the idle control valve right up on the manifold in the center of the engine.

It could, however, be a badly out of adjustment fuel mixture or a bad fuel distributor, and you will have to have the correct tools to find that out -- pressure tester, duty cycle meter, etc.

If you cannot do this yourself, you will need to have a service technician look at it.

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!