The Mass Air Flow (MAF) sensor is located between the air filter and the throttle body. Unlike the MAP sensor which measures pressure, the MAF sensor measures the actual mass (weight) of the air entering the engine using a heated wire element. This provides a very precise reading for the ECU to calculate the correct air-fuel ratio. Because it relies on a delicate heated wire, it is highly sensitive to dirt and oil contamination (often from low-quality air filters), which can cause the engine to run lean or stall at idle.