1998 BMW emits black smoke

Dear Doctor: I own a used 1998 BMW 323ic with 130,000 miles. When I start it in the morning black smoke emits and the car runs rough. If I open the oil cap the rpms go up and the smoke stops and the car runs better. The engine light codes are reading P1188 and P0170. When I drive about 8-10 miles the transmission light comes on and it shifts from 2nd to 3rd gear with a bang. It also bangs when I stop. I don’t know if the transmission fluid or filter were ever changed. Any ideas? Al

Dear Al: There is no question that you have a vacuum problem in the crank case system. You need to find a shop or dealership with a technician who is knowledgeable on your model-year BMW. Your car has a plastic intake manifold and many vacuum connections and valves that will place some vacuum into the crankcase. When you take off the oil cap you are letting in additional fresh air. The trouble fault code 1188 refers to fuel control banks 1. The p0170 is a lean condition. — Junior Damato, Ask the Auto Doctor

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