A Dive under the Hood: The Mass Air Flow Sensor

Almost all modern cars come with an electronic fuel injection system, which is comprised of a variety of complex components. One such critical component is the Mass Air Flow sensor (MAF). Installed between the intake manifold and the air filter of the engine, the mass air flow sensor’s job is to measure the air flow (the amount of air entering the engine).

The mass air flow sensors you find in modern cars have built-in Intake Air Temperature sensors (IAT). While there are different types of air flow sensors, most cars today come fitted with the hot-wire type. Let’s find out how it works.

Hot-Wire Mass Air Flow Sensor: How it Works

A hot-wire mass air flow sensor basically consists of a small electrically heated wire, and a temperature sensor, which measures the temperature of the air surrounding the wire. When the engine is on idle, the amount of cool air flowing around the hot wire is low, which means a low amount of electrical current is required to keep the wire hot. However, when the gas pedal is pressed, the amount of air flow over the hot wear increases, and more current is required to keep the wire hot. The amount of airflow is proportional to the electric current.

The air flow sensor also houses an electronic chip which converts the electric current into a digital signal and delivers it to the PCM (the engine’s computer). Using the signals, the PCM then calculates the optimal amount of fuel to be injected. The main objective is to keep the fuel/air ratio at the ideal level.

Furthermore, the PCM determines the shift points in an automatic transmission based on the signals it gets from the air flow sensor. If the sensor develops an issue, it’s likely to impact the automatic transmission as well.

Common MAF Issues

MAF sensor problems are prevalent in many cars, including Volkswagen, GM, BMW, Nissan, Toyota and Mazda, to name a few. In many cases, a malfunctioning mass air flow sensor causes the engine to crank but not start.

A collapsed or an incorrectly installed air filter can lead to an air flow sensor failing prematurely. Other causes of air flow sensor trouble include over-soaking a washable air filter.

Signs of a Faulty Mass Air Flow Sensor

Some common symptoms of a failing mass air flow sensor include:

  • Failure to start
  • Stalling
  • Poor acceleration
  • Irregular power delivery
  • An altered shifting pattern (automatic transmission only)
  • Check Engine or Service Engine light coming on.

Timely preventive maintenance and repairs are important if you want your vehicle to live a long healthy life. Schedule an appointment with Smitty’s Auto Service, one of the best auto repair shops in Gainesville, FL. and our highly skilled automotive technicians will ensure that your vehicle continues to perform optimally. Get in touch with us at (352) 373-3060 for further information.


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