In a car, the coherence of all processes is important, which depends on the correct operation of internal systems. Let’s figure out what a mass air flow sensor is and why it is needed
What is Mass Air Flow Sensor “MAF”?
MAF (mass air flow sensor) is a thermoanemometric device from the category of electronic systems, designed to assess the volume of air masses that enter the internal combustion engine. In everyday life, it is often called a flow meter. MAF appeared in the 1980s along with controlled software injection systems.
The flow meter is connected to the electronic engine control unit. Modern cars use two types of MAF, which are located in the intake system:
The operating principle of the sensors varies depending on the design:
Thread sensors provide more accurate information – 3% better than film ones. But the latter are much simpler and cheaper to produce: there is no need to attach threads by welding or fix them on hangers.
What is the MAF for?
As the name suggests, the device is designed to measure air flows. The signal from the air mass sensor is used:
- to calculate the required volume of fuel and the engine operating point;
- in diesel engines – to control exhaust gas recirculation;
- to determine and use the required volume of fuel;
- to calculate the engine load, which results in optimized control of the ignition timing angle and, accordingly, the torque of the power unit.
A stoichiometric mixture, i.e. an optimal ratio, is almost 15 parts air and one part fuel. The MAF is needed to control these two components: data on air volumes is sent to the injection control system. If the sensor is in good condition, it will not only control the fuel supply, but will also reduce fuel costs and reduce wear on the internal parts of the car.
Where is the MAF located?
Typically, the air flow meter is located just behind the air filter and in front of the engine intake manifold. The sensor may also be located elsewhere in the intake manifold, but it is always in front of the throttle body. This location allows it to measure the amount of air entering the engine. Based on the sensor readings, the ECU calculates the amount of fuel to use.
Sometimes the air temperature sensor is combined with the MAF. However, there are different types of flow meters, and they all require individual maintenance. Digital systems send a frequency output signal, while analog MAF sensors produce a variable voltage signal. Both outputs are sent to the engine control module to help regulate the air-fuel mixture in the vehicle’s automatic transmission system.
The air entering the manifold can be recorded by another sensor, the MAP sensor, which works together with temperature control. The MAP sensor, unlike the MAF sensor, measures the difference in pressure in the vacuum chamber and at the input. It has a highly sensitive diaphragm. It stretches, thereby changing the resistance of the strain gauges.
Signs of a faulty MAF
Due to incorrect operation of the air flow meter, the control unit will not receive current data on fuel consumption, as a result of which there may be insufficient or, conversely, too much fuel. It is not always possible to determine the exact cause by indirect signs. Thus, similar malfunctions occur when the ignition system or turbocharger does not work correctly. Take a closer look at the main and indirect “symptoms” and solve the problem with the help of a specialist:
Error on the instrument panel
If the MAF fails, the Check Engine indicator sensor is triggered. At the same time, the engine power decreases. The error code is stored in the system to simplify further diagnostics. When there is no on-board computer with the ability to determine the cause of the malfunction, you will have to solve the problem at a service center.
Increased fuel consumption
If there were no breakdowns, but the engine suddenly began to consume more fuel, the cause may be a sensor failure. The same problem is indicated by dips when shifting gears, loss of traction or, for example, starting the car not on the first try. When the MAF gives a weak signal, fuel consumption can increase by up to 20%.
Working voltage
Try connecting a multimeter for measurements. Ideal output voltage readings are 0.996 V. Lower readings indicate different degrees of wear. If the resource is coming to an end (readings are less than 1.040 V), the sensor will need to be replaced soon. Keep in mind that the accuracy of the data is affected not only by the condition of the part, but also, for example, by poor crimping of the wires.
How to check MAF
The MAF is checked at every maintenance or at the customer’s request, the check is carried out using the official GAC program. Average cost of the service:
It is impossible to refuse the MAF, without it the engine control module will not be able to calculate how much fuel to supply. The consequence will be uneven operation of the internal combustion engine and the lack of actual engine power.
This sensor needs to be replaced if one of the resistors has failed. Cleaning is very rarely required if the readings start to differ from the base ones.”
The only downside of the mass air flow sensor is its price. The cost range is very large, from 3 to 30 thousand rubles depending on the car and manufacturer. In some car models, the MAF is built into the engine control unit. Then replacing it will be much more expensive.
