You don't have a choke, you have D-Jetronic fuel injection.
Several possible causes, most likely rich running (hence the black smoke).
Several possibilities here
-- bad ignition (plugs, wires, points (yes, you do have points), cap, rotor.
-- bad connection on the air temp sensor in the air intake horn (check for bad wires or a poor connection, or an open thermistor).
--bad MAP sensor, causing serious rich running. Can only be tested for resistance of the two windings, but the usually failure is the anaeroid inside goes bad and it no longer responds to pressure changes.
-- bad temp sensor or bad thermo-time switch for the cold start valve.
If it blows black smoke at full throttle, you need to have the mixture checked. If it cannot be set, check the temp sensors, and if they are good, you will have to replace the MAP.
I'd also run a bottle of Techron or RedLine injector cleaner through it, especially if it has been sitting undriven much -- this will clear the injectors and fuel pump. Don't start "fixing" things until you run the injector leaner and a couple tanks of fresh premium thorugh it!
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!