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Fuel System Home Page > Parts of the Fuel/Engine Management System > Mass Air Flow Sensor

Function: Measures the amount of air entering the engine to determine the most efficient air/fuel mixture for achieving clean burns.

Signs of Wear: Engine hesitation, stalling, decline in engine performance, "Service Engine Soon" light illuminates.

The type of mass air flow sensor shown in this animation is referred to as a hot wire air flow sensor. In this type of system, a bare wire is located in the path of the incoming intake air. As current flows through the wire, it heats up, increasing its resistance. As air flows past the wire, the wire is cooled, decreasing its resistance and increasing the flow of current. Based upon this change in current flow and the signal from the intake air temperature sensor, the engine computer determines how much fuel to mix with the air entering the engine.

Since mass air flow sensors are located in the incoming air stream and the air filter does not filter out 100% of the contaminants, the wire on the mass air flow sensor may eventually become dirty. Sometimes the sensor can be cleaned with special intake cleaner and returned to normal operation. However, where cleaning is unsuccessful or not possible, a defective sensor will need to be replaced. Some mass air flow sensors should not be cleaned.

When a mass air flow sensor becomes defective, it is unable to accurately measure the amount of air entering the engine. As a result, the engine will run poorly and even in some cases, will not run at all. Defective mass air flow sensors usually illuminate the check engine light for air flow problems or misfire problems.

Have your vehicle fuel and engine management system checked by an ASE Certified Technician in Fuel System Services. Set up a reservation today to visit our repair facility on the southwest side of Houston.

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