Question

2005 BMW X3 3.0L M54 with engine code P0171. Engine start with smoke exhaust. sometime come out with misfire code.

Answer 1

P0171 Fuel trim lean Bank 1

Bank 1 for the X3 is cylinder 3,4,5. What cylinder has coded the misfire code? What you can do is take the igntion coil and move it to a different cylinder and see if the misfire moves to that cylinder, this indicate that the coil is faulty.