Po171 code help

Question

My po171 code won't go off it is causing misfires when accelerating until I turn off my car. It used to have po174 and other codes but I have replaced the Mass air flow meter, bank 2 oxygen sensor 1, and I have had smoke tests done to replace the leaking hoses. I am wondering if it could be the bank 1 o2 sensor since it hasn't been replaced and it is throwing a bank 1 too lean. Any advices would be appreciated. Thanks!

Answer 1

Bank 1 Sensor 2 is the downstream 02 sensor all it does is monitor the catalytic for efficiency , A leak down test would be the best way to go, if a lean condition was caused by the PCV or oil cap you would both bank go lean, when it comes to a BMW if there was a overheated engine condition that resulted in a headgasket this is where a lean code would set, and the cooling system would be overpressurized,