BMW Repair Questions? Ask a Mechanic for Answers ASAP
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Most often this is due to a failing turbo. One of the best tests is to inspect the turbo impellor to see how much oil is building up around the impellor and if the impellor has play. It was a good idea to replace the air valve unit first. One additional step you may want to consider before replacing the turbo would be to have the system cleaned of oil. Often oil build up in the piping, intercooler, and intake manifold. This can lead to the same symptom of smoking even after the CCV is replaced. It would be worth having the system cleaned out by removal and cleaning before replacement of the turbo, unless a problem is found in the impellor or if there is a build up of oil around the impellor inside the turbo. If decide to move ahead with the turbo it would also be a good idea to clean the system out to remove all of the oil that has built up.
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