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Air Flow Metre aka Air Mass Sensor - What Are the Symptoms or Signs of It Failing?

Technical  ·  November 26, 2018

Air Flow Metre aka Air Mass Sensor - What Are the Symptoms or Signs of It Failing?

The mass airflow sensor, commonly referred to as the airflow metre, is undoubtedly one of the least known parts of a car and one of the components that get little attention from car owners. It is part of the electronic fuel injection in internal combustion engines that do not use carburettors. 

Sounds mind-boggling? Do not worry, CarPartAU experts are here to shed light on the air mass sensor and what it does.

What is the function of a mass airflow sensor?

As you probably already know, for internal combustion to take place in the engine of your car, oxygen is needed. More specifically, for optimal combustion to take place, a precise balance of air and fuel is required. As the driver accelerates or decelerates, the throttle plate/butterfly in the throttle body opens or closes, allowing in more air or less air respectively in response to the driver's action. With this increase and decrease in the air intake, the amount of fuel injected needs also to vary accordingly to maintain the specific balance of air and fuel. To facilitate this variance, this is where the AFM (air flow metre) comes in. 

As the throttle body let in the air in response to the driver's push on the accelerator, the AFM measures the mass of air intake and sends this information to the vehicle’s Electronic Control Unit (ECU). The ECU interprets the data on air mass flow rate and, in return, communicates the correct mass of fuel to be injected to achieve the required air-fuel ratio for optimum fuel combustion.

There are several types of airflow sensors, and their primary differentiation is the technology they apply to measure the mass of airflow. Here are the different types:

Symptoms of Bad or Damaged Mass Air Flow Sensor

Unfortunately, the mass airflow sensors are not damage-proof, and at times they malfunction. When they malfunction, they send the wrong information to the ECU, leading to the injection of an incorrect amount of fuel. You will know when this happens by watching out for the following signs and symptoms:

Handy Hint: Unlike in the earlier days, diagnosing a faulty air flow sensor is now a quick process. An engine expert with the right tools can easily detect a defective air mass sensor and repair or replace it within an hour or so. This advancement beats the old days when pinpointing an engine problem used to be a trial-and-error thing and different components of the engine had to be tested to find out the exact problem with the car.

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