The Air Flow Sensor or Mass Airflow Sensor (MAF) is one of the components of an electronic fuel injection system and is found in many of modern vehicles. Most mass air flow sensors are one piece hermetically sealed units with no moving components.
The Mass Air Flow sensor is used to measure (actually weight) the amount of air entering the engine. This measurement is used by the engine computer or ECM to calculate proper amount of fuel injected into the cylinders in order to provide optimum combustion and low emissions.
BMW 330 (E46) Mass air flow sensor requires no regular maintenance. On mass air flow sensors with a sense wire, this wire can become contaminated with dust particles. These particles can be removed with automotive solvents that are safe for the use on mass air flow sensors. BMW 330 (E46) mass air flow sensors are commonly misdiagnosed. Before replacing the mass air flow sensor check for air leaks in the connecting air ducts and intake manifold. These leaks can cause similar symptoms as a malfunctioning mass air flow sensor.
Problems with Mass Air Flow sensors are common. Bad or contaminated BMW 330 (E46) Mass Air Flow sensor can possibly cause a wide range of various vehicle drivability problems such as stalling, especially when the engine is cold, misfiring, poor acceleration, etc. In addition, a problem with the Mass Air Flow sensor often causes the "check engine" or "service engine soon" light in the vehicle instrument panel to illuminate.
MAF, Air Flow Meter
The BMW 330 (E46) Mass Air Flow sensor is usually installed in the intake air duct between the air filter and the throttle body mounted on the intake manifold. Some mass air flow sensors are mounted directly to the throttle body.
Depending on the year and options your BMW 330 (E46) has, the above information may not apply. Consult with a professional automotive technician or manufacturer for specifics on your BMW 330 (E46)