Explorer 4WD V6-245 4.0L (1991)
Mass Air Flow (MAF) Sensor: Description and Operation
Mass Air Flow Sensor
The Mass AirFlow (MAF) sensor, located between the air filter and the throttle body, is used to measure the mass of the air entering the engine due to
volumetric displacement.
The MAF sensor operates on the principle that if a mass is maintained at a constant temperature above the ambient environment, then the thermal loss is
proportional to the mass flow of the cooling medium it is subjected to.
The electronic module of the MAF sensor heats a wire element to 392°F (200°C) above ambient temperature. As air passes through the sensor, the air
cools the wire element. The MAF sensor supplies more power to the wire to keep it at a constant temperature difference. When a drop in power useage
occurs, the MAF sends a signal to the Engine Control Assembly (ECA) indicating the drop. The signal increases with the airflow into the engine.