The 1989-1995 BMW models, including 318i, 318iC, 318iS, 318ti, 323i, 323iC, 323iS, 325i, 325iC, 325iS, 325iX, 328i, 328iC, 328iS, and Z3, utilize two types of Mass Air Flow (MAF) sensors: There are two kinds of air flow measuring equipment: a vane-operated electro-mechanical piece and a fully electric device. This sensor works through a moving vane that adjusts a potentiometer, which sends a 5-volt reference to the control unit, plus includes a temperature sensing device for accurate operation. When either parts in this system break, the control unit automatically switches to programmed engine settings for safe driving. Since the MAF sensor has no working parts besides a wire, it uses electronic readings to tell the ECM the amount of air entering the engine. The ECM changes how long the injectors send fuel to make sure we mix exactly the right amount of fuel and air, even when environments change around us. In cars with Automatic Slip Control and Traction, another throttle valve is linked to an electronic motor that controls traction. The MAF sensor has a hot wire element that can easily break, but while you can clean or convert the screen, you can't fix or replace any other parts. Check the MAF connection for 5-volt reading through either a BMW service tester or Data Scan Tool, or do it yourself with a digital voltmeter. Uninstalling the sensor requires several steps: switch off the engines power, loosen and detach hose clips, disconnect power wires, remove the air filter unit, return the sensor, and close everything back up.
Posted by BMWPartsDeal Specialist 
