BMW Repair: Check Engine Light keeps coming on!!!, crankcase ventilation, gasoline usage

Question
Hi i have a 2003 330ci with 48,000 miles. The check engine light keeps coming on. I had the fault scanned and it told me that the monitor o2 sensors were faulty and i had misfiring. Sometimes when the light came on it said just the o2 sensor error So i changed all the o2 sensors figuring that it was causing the misfiring. The light came back after 80 miles still saying o2 sensors and random misfiring cylinders 3-4-5-6?.... Do you have any ideas????

Answer
Paul, engine light is coming on probably because of a fuel mixture issue that is being detected by the O2 sensors. The O2 sensors will store faults for mixture adaptation limit being reached. They can no longer correct for the imbalance in fuel mixture. You need to figure out what is causing the misfire. My bet is a mixture related problem. You need to figure out whether the mixture is too lean or too rich. There are so many causes for mixture problems it is impossible to list them all. Common ones are Leaking intake system, Leaking Crankcase Ventilation system. Fuel filter issues from poor gasoline usage. Faulty Mass Airflow reading. Best to have the problem diagnosed if you are unfamiliar with how to test or replace these items.
-Evan