Mass air flow meter or MAF sensor: what it is and how it works

Although it is one of the great unknowns among all engine components, the mass air flow meter or MAF sensor is essential for monitoring the proper functioning of the engine. This device is located behind the air filter, and its function is to control the intake of air into the engine so that the combustion takes place in a controlled and efficient manner. Its correct operation allows the engine to run well and not consume more fuel than necessary.

Very often the mass air flow meter goes unnoticed and is not considered until it begins to fail and the mechanic informs us that the fault originates from it. If the mass air flow meter, also known as the MAF sensor, malfunctions, the amount of air entering the engine is not the right one and may prevent correct combustion, potentially causing serious engine problems in the medium term. Immediately, a loss of engine power will be noticed.

What is the mass air flow meter?

The MAF sensor or mass air flow meter is made up of three main elements: the thermistor, a platinum wire and the electronic control circuit. These three elements make it possible to regulate the flow of air to the engine and keep everything working properly. The system determines the amount of air needed for combustion to occur correctly, with the precise quantity of fuel, and to avoid excessive pollution.

The mass air flow meter works thanks to the heating of the platinum wire. This reaches a temperature of 200 °C and maintains it constantly throughout the journey. The air passing through the flow meter cools it, and in this way the system supplies more current to keep the wire at a constant temperature. Thanks to the amount of energy used to heat the flow meter, the on-board computer, the ECU, knows the quantity of air reaching the engine.

Another point to consider is the temperature of the air passing through the MAF sensor. If it is very cold, it will cool the wire more quickly. To know exactly the temperature of the air passing through this component, the thermistor is used, which measures this value and helps establish the air needed for proper operation.

With all the data obtained, the ECU knows how much air it needs to inject into the engine so that it runs correctly. The mass air flow meter is essential for the proper operation of the engine, so it requires close attention. When it fails, the engine fault warning light comes on. This is due to poor combustion of petrol or diesel and appears in the scan as one of the errors to be resolved.

Mass air flow meter maintenance

The mass air flow meter does not require continuous or exhaustive maintenance, but if it causes problems it must be checked. The platinum wire may have broken, so the amount of air entering the engine cannot be controlled. It is also possible that the gaskets are damaged and more air than advisable enters the engine. Another possibility is that the cables running from the flow meter to the computer are faulty and need to be replaced.

If there is a problem with the mass air flow meter, the car must be taken to the workshop and the mechanic must determine the condition of the flow meter and what the problem may be. If it can be repaired, the mechanic can replace the parts needed and make it work normally again. If it cannot be repaired, it can be replaced. The price of a new flow meter varies according to the type and model of car, but it is not a particularly cheap fault, so for any problem, it is advisable to go to the workshop and have it repaired.

Types of mass air flow meter

There are several types of mass air flow meter, depending on the technology they use. Here are some of them.

• Air vane flow sensor: This type of sensor works with a vane that allows or prevents the passage of air through the action of this movable flap.
• MAP sensor (Manifold Absolute Pressure): The air flow is regulated by a system that converts it into electrical impulses, allowing the ECU to know how much air is circulating and to control it.
• Hot wire sensor: This is the most common of all and the one used in most models. It works exactly as described above.

All these types of mass air flow meter allow the engine of our car to work correctly, ensuring a proper balance between fuel, air and spark, so that the car delivers maximum performance and produces minimal polluting emissions.