Would not hurt to add some injector cleaner for diesels to a full tank of fuel. The smoke and roughness could be uneven spraying injector nozzels. Any large truck stop will have it. If the temperature gauge is within the normal range upon restart, just turn the key like any other car and start it. No need to warm an already warm cylinder.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.