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Q: Check engine light

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O2 sensors (running Lean) and now blue smoke has been coming out of tailpipe not all of the time.

My car has 75000 miles.

A: The engine running lean could be due to usi...

The engine running lean could be due to using the wrong air filter and or the mass air sensor is defective. Check to see you are using the correct air filter and replace it if you are not using a factory filter, before the mass air sensor is replaced. The smoke you see may be the engine using extra oil from the restricted intake air filter. This causes the engine to suck in excess oil into the cylinders and puts it out the tail pipe. It's also possible that you have overfilled the engine oil. I recommend having the systems checked by a mechanic with the correct scanner for your BMW. They will be able to look at the O2 sensors fuel control before and after the filter is changed. Also, the technician will check if the mass air sensor is in need of replacement in order to sort out your Check Engine Light.

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