i have a 1981 240d with appx 150k. for about a month i have noticed substantial lack of power with car and lots of smoke on startup. took to a mechanic today and they say that one of the cylinders is not turning or does not have power and the other three cylinders are having to push it. raw fuel and oil is being dumped into this cylinder. What causes this and can it be fixed and for what price? Any replies are gretly appreciated as I love this old car and hope I can save it!