Mass air flow sensor. How does it work. Main features and device of the air flow sensor What does the air flow sensor answer?

Listening to auto mechanics' diagnostic results and repair forecasts, very often the mass air flow sensor (mass air flow sensor) is mentioned as a possible cause of the malfunction. It is practically beyond repair, and replacement costs a pretty penny. Sometimes, after making a replacement, it turns out that the breakdown has not disappeared and the check signal still cheerfully informs us about problems in the engine system. Therefore, correct diagnosis and correct understanding of the sensor’s operation will save time and money for the car enthusiast.

Mass air flow sensor - what is it, the function of the mass air flow sensor

The only function of an expensive sensor is to measure changes in the force of air flow entering the internal combustion engine. It is a mistake to think that the sensor regulates the air flow. Based on the meter readings, the engine ECU (on-board computer) regulates the flow of fuel, achieving the optimal composition of the fuel-air mixture.

In the latest models of foreign passenger cars, the meter is supplemented with correlating sensors for temperature and atmospheric air pressure. The readings of several sensors help control the ignition timing, increasing engine efficiency.

The mechanism of operation of the flow meter, the design of the mass flow sensor

The operation of common sensor models is based on measuring the electrical power required to maintain a stable temperature of the heated element of the device. In older designs (pitot tube vane flowmeters), a potentiometer measures the degree of blade bending.

The main designs of flow meters are equipped with hot-wire meters with wire, plate, and film elements. When the ignition is turned on, the refractory element of the flow meter heats up, sending the ECU an initial signal. Opening the throttle valve causes additional air flow, cooling the hot-wire anemometer. The sensor measures the electrical voltage required to additionally heat the element. This value becomes a calculation indicator for determining fuel injection. The high price of a wire meter is due to the presence of precious metals (platinum) in the mechanism and the precision assembly accuracy.

The operation of a membrane flow meter is based on similar principles. The signal to the electronic control unit records the temperature difference on the sides of the membrane, since the inner side cools more slowly.

Structurally, the air flow meter consists of a plastic cylindrical pipe, inside of which a hot-wire anemometer meter is mounted. Air is drawn in through a grille deflector (metal or plastic) equipped with rubber O-rings. The electrical circuit connector with power supply wires and signal to the ECU is located on the outside of the device. The device is placed between the air filter and the engine.

Causes of malfunction, signs of failure

The main reasons for the malfunction of the mass air flow sensor are natural wear (combustion) of the wire, meter membrane, and contamination of the hot-wire anemometer. Damage to the device can be caused by extreme modes of vehicle use, long-term operation, and rare air filter replacements. A clogged filter allows oil and resins to pass through to the flow meter, which are deposited as a film on the wire or membrane, distorting the readings.

Signs of a malfunctioning meter include:

1. Changes in engine speed at idle.
2. The “check” signal appears on the on-board computer display.
3. Dips in engine power when using the accelerator.
4. Engine stops while moving.
5. Increased fuel consumption.

Such symptoms cannot be considered an unambiguous indication of a breakdown of the flow meter; similar symptoms occur when the throttle valve, USR valve, fuel pump, or ignition module malfunction. A final answer is only possible by diagnosing the meter.

The ECU responds to failures in the flow meter readings by switching the engine to emergency mode. Based on the readings of the crankshaft and throttle position sensors, the control unit supplies the engine with a supersaturated mixture, worsening power and economic performance.

Self-test of the sensor

To independently check the electrical signals of the flow meter, which is not particularly difficult, you will need a multimeter. The first stage is diagnosing the functionality of the detachable connection (chip). To do this, use the positive probe of the tester to check the red-black connector on the removed chip. By attaching the second probe to the cleaned motor bolt, we compare the voltage readings in the network. If the readings coincide with the battery charge, we can talk about the serviceability of the chip.

The standard pinout of flow meters manufactured by Bosch, used in many VAZ models, uses the following colors (by location from the windshield):

1. Light yellow. Signal input.
2. Grey-white. Sensor power cable.
3. Green. Grounding the flow meter.
4. Pink-black or white. Signal to the ECU.

Having connected the connector to its original place, we check the readings with the engine not running. The mass probe remains in the same place during further tests. By inserting the positive probe into the fourth wire, we get readings of the transmitting signal to the computer. The standard signal voltage of a working flow meter ranges from 1.0 - 1.02 volts. Readings above 1.05 volts indicate the need to replace the sensor.

At idle speed (the engine needs to be warmed up), the standard readings vary from 1.2 to 1.8 volts. To check the efficiency of the mass air flow sensor, we check the readings by opening the throttle valve several times. An increase in engine speed should cause an increase in signal strength.

Maintainability of the device

Vane sensors are considered conditionally repairable, although almost all auto mechanics refuse to repair them. Real repair of the flow meter comes down to replacing the device assembly. The operations of dismantling and installing the device are simple; the cost of replacement is increased by the need for several types of diagnostics and checking other components that cause identical engine behavior. The selection of a replacement sensor should be trusted by an experienced auto mechanic who knows the features of your car model.

To buy a replacement sensor you will need to spend 4,000 - 9,000 rubles (depending on the design of the meter and the car model). Therefore, you can try to clean the device yourself, which is practiced by many car enthusiasts.

Cleaning the sensor as an alternative to replacing the flow meter

The need for cleaning can only be determined by completely disassembling the sensor. To dismantle the flow meter, you need to disconnect the six-pin plug of the detachable connection, the air intake corrugation clamp (you will need a shaped screwdriver), and two bolts securing the sensor to the air filter housing. When disassembling the sensor itself, you need to carefully remove the deflector grille so as not to damage the O-ring.

A visual inspection may show the presence of an oil film, dirt, and traces of carbon deposits on the surface of the anemometer (two wires or a film membrane). When cleaning a delicate device, the greatest danger is represented by the contacts secured with a gel-like compound. They are easy to break, so you cannot use compressed air blowing, cleaning with the tip of a knife, a sharpened match, a toothpick, or cotton swabs.

Numerous experiments have shown that most solvents are unsuitable for washing. Esters, ketones, acetone, strong solvents (“Winns”, “Abro”, “Carboklin”) dissolve the compound and can damage the membrane film. You need to be careful with the recommendations for using WD-40 and Liquid Key cleaner that contain heavy fatty acids. After washing off the deposits, these products leave an oily film on the anemometer.

The best cleaning solution is medical alcohol diluted with water, which is injected several times with a syringe. Heating the mixture (60-70 degrees) will improve cleaning results. You can dry the flow meter using a fan, naturally.

Video: checking the serviceability of the mass air flow sensor

When assembling the sensor, you must carefully install the sealing ring and check the sealing skirt. When the sensor is installed correctly, the arrow on the housing is directed towards the engine. For some flowmeter models, the axial orientation of the sensor is important. If its position is not specified in the manual, you need to mark the correct location of the anemometer during disassembly.

Prevention of air flow sensor

The only effective means of prevention for the flow meter is timely replacement of air filters. Auto mechanics do not recommend regular cleaning of the device; it can only damage the sensitive elements of the device, rendering it inoperable.

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The mass air flow sensor, also known as the MAF, determines the exact amount of air admitted into the engine. The filling of cylinders with mixtures must be controlled. Thanks to the mass air flow sensor, this task is possible. The equipment is considered one of the most important in the injection system and began to be used immediately after its introduction. Located in the intake tract. More precisely: between the intake and. Now we already know where the mass air flow sensor is located, let’s now move on to the principle of operation.

Device operation

The ratio of the amount of incoming gasoline to air per stroke is 1/14. Under these conditions, the engine promises optimal performance. In the worst case, there is either a decrease in power or excessive fuel consumption.

The principle of operation of the sensor is to measure the incoming air and transmit this information to the on-board computer. After receiving the information, the computer determines how much fuel to allocate to the engine.

You can control the amount of air coming in. By pressing the gas pedal harder, more air will enter. Accordingly, there will be more gasoline if the sensor is working properly. Hence the rule: when driving calmly without jerking, the air consumption will be small, and with it the gasoline consumption will decrease.

Let's move on to the design. A platinum wire (70 µm in diameter) is located inside the measuring tube. Ahead of it is the throttle valve. The principle of constant temperature is how the device works. However, there are many sensors on the market, each of which determines the amount of air using its own method and is built in its own way. More on this a little later.

Regarding the platinum wire. Previously, there was constant contamination of the wire after work. To avoid this, the developers installed support for the incandescent wire function in the electronic control unit. Within 1 second after turning off the engine, the surface heats up to 1000 C, and at the same time all remaining dirt is removed. Attempts to maintain the mass air flow sensor in good condition will not exclude the fact that an early breakdown will require a complete replacement of the equipment. Yes, yes, unfortunately, the sensor is difficult to repair and you will need to replace the old one with a new one, but there is still a way out.

Breakdown problems, diagnostics

Fortunately, the signs of a malfunction are varied. It’s easy to find out about a breakdown if you follow the signs indicating it:

• Inscription on the instrument panel. It can indicate a variety of breakdowns, not excluding sensor malfunction.
• The driving dynamics are gone.
• Increased fuel consumption.
• Loss of horsepower.
• Problem with running a hot engine.

And that's not it. Cleaning the mass air flow sensor may be necessary for many other ailments. Oil can drain through the crankcase ventilation, which, when it gets into the surface of the air duct or air filter, disrupts operation, which causes sensor malfunctions.

By the way, illnesses are observed even if dirt gets into sensitive areas of the equipment. The developers are trying to create a design that does not collect a lot of dirt and is very stable when operating in different temperature conditions. Nevertheless, there are cases.

Today there are about 50 variations of mass air flow sensors on the market. As you can see, there is a lot to choose from.

• Vane flowmeters.

The installation is based on a pitot tube. In the middle there is a thin plate, which is fixed quite softly. The plate bends under the influence of air flow. Its bend is registered by a potentiometer, changing the resistance values. The control unit collects information from the potentiometer readings and decides how much fuel is needed.

• With hot-wire anemometers.

This option is more common, which is what we talked about. The design is based on a heat exchanger from which two platinum plates emanate. Current passes through them. The first plate is working, and the second is for reserve. Since the temperature of one plate is always higher than the other, the air flow aims to cool one of them, trying to equalize the temperature. To compare the temperature, more current is supplied to the non-working plate, and it is these indicators that affect how the control unit will react and how much gasoline it deems necessary to release. A low signal level when tested with a multimeter is a bad sign.

• With film meter.

Silicon wafers coated with platinum began to be supplied to the market a couple of years ago. They haven't gained their popularity yet.

Is there a malfunction or not?

To know how to check the mass air flow sensor, one step-by-step instruction is enough. Still, we will look at several options. Let's start with the most effective one.

With the engine turned off, disconnect the sensor connection connector on the on-board system. When the engine is turned on, the system will begin to operate in emergency mode. From now on, the amount of air supplied is not important. The position is important. After disconnecting the mass air flow sensor, try driving the car. If an increase in dynamics is felt, we advise you to take possible sensor damage seriously.

The next check of the sensor is visual. Look in all the nooks and crannies for dried oil, dirt or liquid on the surface. If you find something like this, urgently clean the equipment and also eliminate problems with leaking oil.

For greater accuracy, get a multimeter. Setting the DC voltage measurement - 2 V. Connect the multimeter to the green and yellow wires. Often colors may vary. For accuracy, we will tell you the sequence of connectors - 1 and 3.

With the ignition on and the engine off, the mass air flow sensor voltage is 0.996–1.01 V. Beware if this value exceeds this level. As a rule, with a parameter of 1.05 V you can safely throw away the mass air flow sensor; no amount of flushing will help here.

Agree, it’s so effective. After analyzing the results, you can begin further work.

Disassemble, clean, assemble

We'll warn you right away. The opinion of experts is divided into two sides. Some people think that the procedure is useful, while others are sure that such repairs will only worsen the problem. However, do it carefully and everything will work out.

Prohibited for use:

1. Cotton buds.
2. Acetone.
3. Compressed air.
4. Ethers.

There is a liquid sold on the market that is used to clean carburetors and WD40. It will be a good alternative to a cleaning product.

Now let’s talk about how to clean the structure in order to avoid the cost of buying a new one (a new mass air flow sensor costs about 2000 rubles).

Let's remove the pipe. Without this action, it will not be possible to properly clean the sensor. Star keys of different sizes will come in handy. We unscrew all the bolts and screws and remove the sensor from the pipe.

At this point, you may be surprised to see a huge amount of oil on the surface of the sensor. This is good, because now there is hope to repair the device yourself without buying a new one. With the cleaning liquid we have already talked about, we spray several sensor wires that are held in place by the resin.

Now let's wait until everything dries. If necessary, we carry out a series of actions again. By the way, if you don’t have carburetor fluid, you can use simple alcohol. After cleaning the sensor, take care of the mesh of the pipe and its inner surface. Change the air filter and put everything back in order. The mass air flow sensor readings may change after this procedure.

Now you know how to clean the mass air flow sensor. As you can see, the equipment is very important and fragile. If you carry out inspection work regularly, you can avoid frequent breakdowns!

Mass air flow sensor is a device that determines the quality of the air-fuel mixture in a car. Failure of the sensor will lead to incorrect operation of the internal combustion engine.

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Why do you need a mass air flow sensor and its device?

Explanation of the abbreviation MAF - mass air flow sensor.

A mass air flow sensor is a distribution controller designed to warn the electronic engine module about the volume of air flow entering the combustion chambers at a certain moment. This data is necessary for the efficient functioning of injection engines, since in carburetor units this function is performed directly by the carburetor. The air flow in a car is sucked into the cylinders through vacuum, and fuel is injected by injectors.

Gasoline is always supplied in certain volumes. This function is performed by the electronics system in accordance with the information received from the controllers. The volume of the fuel dose is determined by the position of the crankshaft and its rotation speed sensor. This is also affected by the amount of air flow entering the cylinders of the internal combustion engine. The mass air flow controller allows the microprocessor module to balance the air-fuel mixture and ensure high-quality operation of the internal combustion engine.

Regulator Structural Components

The mass air flow sensor, which affects the operation of the power unit, consists of the following elements:

• body, usually made of plastic;
• the main deflector through which the air flow passes;
• metal screen;
• MAF board or ADC processor, designed to control air volume and process information before sending it to the microprocessor unit;
• connector used to connect the electrical power supply circuit of the device.

In modern vehicle models, this regulator is additionally equipped with corrective temperature controllers. The device can also be supplemented with an atmospheric air sensor. In accordance with the readings of these regulators, it is possible to control the ignition timing. The coordinated functioning of the sensors ensures more economical operation of the internal combustion engine.

Where is the sensor located

The sensor is located in the engine intake tract, usually immediately after the air filter housing. For example, in VAZ cars there is a thick hose or corrugated line after the controller. But regardless of the car model, the flow meter is located near the filter.

What happens if you turn off the mass air flow sensor?

When the controller is turned off, the microprocessor module will automatically go into emergency operation mode. The amount of air and fuel to form a combustible mixture will be formed in accordance with the position of the throttle valve. This will lead to an increase in fuel consumption. The crankshaft will operate at higher speeds, at least 1500 per minute.

It is possible to use the machine with the mass air flow sensor turned off, but this will increase fuel consumption and engine contamination.

Operating principle and types

The action of the controller depends on its type; today there are three types of devices:

• wire;
• film.

Wire

Wire type flow meter

Previously, this type of device was universally installed on all Russian-made vehicles. Its peculiarity lies in the use of additional elements in the design.

This is about:

• ring and holder for it;
• device for CO regulation;
• platinum wire;
• resistor element for temperature compensation.

The operating principle of this mechanism is based on the hot-wire anemometric method. Here the thermistor element is heated by the current that passes through it, so it is mounted in a place where the air flow passes. As a result of its influence, a change in heat transfer occurs, as well as in the resistance value. This makes it possible to determine the required volume of air in accordance with King’s special formula.

When the flow rate through the device approaches zero, the resistance wire is heated to the appropriate temperature. This allows the bridge to be held in a certain state. As the air flow increases, the thermistor element cools, causing the internal resistance to change. Accordingly, an imbalance occurs in the bridge circuit. This leads to the generation of current at the output of the amplifier device, which partially passes through the temperature compensator.

This process makes it possible to calculate the required volume of air mixture taking into account the voltage passing through the bridge. In order for the pulse to be perceived by the microprocessor module, it is converted into a digital signal or analog. In the first case, the ECU determines the flow rate in accordance with the output voltage frequency, and in the second case, according to the level of this parameter.

Wire-type air flow sensors are characterized by one drawback - during their operation there is a high temperature error.

Therefore, the sensors are equipped with additional thermistors. During operation, wire controllers collect dust and dirt. To remove them, the regulator periodically heats up to critically high temperatures, this occurs after the power unit is turned off.

Film

Film type air flow meter

The operating principle of such devices is similar to wire controllers. But the main difference is in the design. Instead of platinum wire, silicon metal is used. This material is coated with platinum plating in several layers. Each of them is used to perform a specific role.

In particular, such devices have three layers of platinum coating:

• temperature;
• heating;
• thermal resistance layer.

The crystal itself is mounted on a protective casing and installed in a special line, through which the flammable mixture passes. The channel design is designed so that the temperature is measured not only from the flow at the inlet, but also at the outlet. This allows for high air speed, but prevents dirt and dust from depositing inside the sensor itself. When the engine starts, the heating element warms up to maximum. The thermocouple of the device is cooled by air flow, this allows for correct measurements of the volume of the mixture.

The outgoing pulse can be analog and converted through the use of an ADC to digital. Compared to wire controllers, the error of film controllers is approximately 4%. But the popularity of these devices is high due to the low cost and wider functionality of microprocessor modules.

User Ivan K talked about the use of film flow meters.

Signs and causes of malfunctions

The need for diagnostics may arise with the following “symptoms”:

• a “Check Engine” indicator appeared on the control panel inside the car;
• an error appears associated with a reduced signal level of the air flow controller;
• the power unit began to start poorly, starting every once in a while;
• the engine accelerates slowly, stalls for no reason, a drop in power is felt when driving uphill and on a flat road;
• fuel consumption has increased;
• the power unit functions unstably at idle speed;
• the motor may stop randomly when changing gears;
• The engine speed fluctuates, sometimes increasing, sometimes falling.

A controller malfunction may be due to the following reasons:

• break in the regulator circuit;
• breakdown of the sensor itself;
• damage to the ground in the wiring, presence of oxidation on the contact;
• the device is clogged with dirt;
• breakage of signal conductors or their incorrect connection.

User Demoin626 spoke in detail about the possible causes of failures in the operation of flow meters.

Sensor check

You can check the operation of the controller in several ways; first, test it:

1. The engine compartment of the car opens. The power wiring is disconnected from the air flow controller. The hood closes.
2. The power unit is started, at this moment the engine should automatically switch to emergency operating mode. An indicator may appear on the instrument panel indicating a problem with the internal combustion engine. The volume of air to form a combustible mixture will be supplied to the engine cylinders in accordance with the position of the throttle valve.
3. A trip is carried out in the car, the dynamics of the car are checked in comparison with what it was before the sensor was turned off. If the car begins to move more confidently and its power increases, this indicates a malfunction of the flow meter.

Testing using a tester

The diagnostic procedure can be carried out using a multimeter. Its black probe is connected to ground or ground, and the red probe is connected to the sensor signal input. You can find out more about the pinout in the technical documentation for the flow meter. The passport must also indicate the technical parameters that will be required for testing.

The multimeter or voltmeter is set to measurement mode in the range of two volts. The ignition is activated and technical parameters are measured. If during the diagnostic process the tester does not show any values, you need to make sure that the probes are connected correctly to the ground and the device signal.

As a result of diagnostics, the following parameters may appear:

• 0.99-1.01 volts - this indicates that the controller is functioning properly;
• 1.01-1.02 V - the flow meter is working, its condition is normal;
• from 1.02 to 1.03 volts - the device is working, but may require replacement soon;
• 1.03-1.04 V - the flow meter condition is close to critical;
• 1.04 - 1.05 - the device is almost out of order;
• readings greater than 1.05 indicate the need to replace the flow meter.

The “Autoelectrics HF” channel spoke in detail about the procedure for testing the air flow regulator using a multimeter.

Visual diagnostics

External inspection of the air flow controller is a less accurate option, but the simplest in terms of implementation.

To do this, you need to dismantle the sensor and assess its condition. A malfunction of the device will be indicated by mechanical damage, as well as the presence of liquid inside. If there are traces of grease in the flow meter, this indicates incorrect adjustment of the oil supply system to the power unit. If the device is heavily soiled, the air filter element must be replaced or cleaned. If you have a working flow meter, you can install it instead of the existing mass air flow sensor.

How to troubleshoot?

There are two ways to get rid of problems in engine operation if they are related to the flow meter - by changing the device or cleaning it.

Replacement

The controller changes like this:

1. The car's ignition is turned off and the hood opens.
2. The block with cables connected to the flow meter is disconnected.
3. The inlet hose that comes from the air filter element is disconnected. To do this, you need to loosen the fixing clamp in advance using a Phillips-head screwdriver, as shown in the photo.
4. Using a 10 mm wrench, unscrew the two screws that secure the flow meter to the housing of the filter device.
5. The controller is being dismantled.
6. The tightness of the sealing element at the location where the flow meter is installed is diagnosed. If the ring is worn out, it is replaced.
7. A new controller is installed and securely fixed to the filter device. The hose is put back onto the flow meter body and the clamp is tightened.

Loosening the clamp on the air flow pipe of the mass flow sensor Disconnecting the power supply from the flow meter Removing the device from the seat

Cleaning

The inside of the controller may be covered with traces of oil; when cleaning, you need to get rid of this layer. To accomplish this task, you can use a carburetor cleaner. There is a film inside the flowmeter, on which there are several sensors made in the form of wire. They are fixed to the device using a special resin. You need to take the product and carefully spray it on the sensitive component so as not to spoil it.

Then you need to wait a few minutes until the liquid dries. The cleaning procedure is repeated as many times as necessary to completely remove contaminants. To speed up this process, you can additionally use a compressed air cylinder, which will be used for drying. If there is no carburetor cleaner, other means, for example, alcohol, can be used. In addition to the flowmeter itself, it is necessary to remove dirt from the internal surface, and debris and dirt from the device’s pipe are also removed.

How to deceive the DMRV?

To bypass the flow meter, you can install a diode instead; this is a kind of deception. For this device to work correctly, the power unit of the machine must function without interruption. If malfunctions appear in the engine, there will be no point in using blende.

To complete the task, you will need a diode element with a drawdown of 0.3 volts. The essence of its installation is to deceive the microprocessor module of the engine. You can buy such a part at any radio electronics store. The device will be used to send from the reference five volts to the signal 4.7 V. As a result, the microprocessor module will consider that the flow meter is recording a large volume of air flow.

The air flow sensor is necessary for the engine management system to organize proper operation. It allows you to track how much air has passed to the throttle valve from outside. The signal generated at its output is fed to the electronic control unit. The latter carries out processing and, according to the underlying algorithm, calculates the required amount of gasoline for proper injection operation. Failure of the sensor disrupts the functioning of all systems. The engine runs erratically because the electronic brain cannot understand how much fuel the engine requires.

Basic functions of the sensor

As stated above, it determines the exact amount of air consumed by the fuel system. Not pure gasoline enters the combustion chambers; it is mixed in a ramp with air; the ideal proportion is 1:14, respectively. When powered by such a mixture, the engine operates in normal mode and is capable of delivering high performance. When the proportion changes, the engine loses power, and gasoline consumption also increases significantly.

Consequently, the VAZ-2110 air flow sensor, for example, allows you to determine the amount of air that has passed into the fuel rail. The joint operation of all measuring instruments, such as throttle position sensors, crankshaft and camshaft sensors, speed, pressure, allows the engine to normalize. By collecting all the information, it is possible to ensure uninterrupted operation of the motor under various loads.

The operation of the mass air flow sensor as an example

Imagine that you are driving a car. To increase speed, you need to press harder on the accelerator pedal. At this moment, many processes occur, and all characteristics change. If you open the throttle with the pedal, more gasoline flows. The more it goes into the combustion chambers, the more air is required to create an ideal air-fuel mixture.

To properly mix air with gasoline, a sensor is installed in the engine intake system. But for proper operation it is required that the air supplied is as clean as possible, without dust and other small particles. A filter is provided for this purpose. Another situation: you release the gas pedal, intending to reduce speed. If you supply the same amount of air as at high speeds, the engine will stall. The VAZ air flow sensor allows you to avoid this, if you already started giving an example on the “ten”.

Sensor device

The basis of the measuring device is a plastic tube through which air passes. It contains a thin platinum wire (its diameter is about 70 microns). When the engine is running, this wiring heats up. The temperature of the wire during operation fluctuates around one hundred degrees. There is nothing complicated, as it might seem, in the design. The wire warms up, and the change in its temperature shows how much air has passed through the tube.

All this is calculated according to the algorithm embedded in the central control unit. The design also has resistors, which are necessary to stabilize the operation and adjust the current values. It is against this parameter that measurements are made. It is worth noting that the air flow sensor, the price of which on average is about 2000 rubles, contains a precious metal - platinum. The central wire and mesh are made from it. There is nothing to replace platinum, so there is no hope that the price of the device will fall. And if a malfunction of the air flow sensor occurs, its resuscitation is almost impossible.

How the device works

Having dealt with the device, in which there is nothing complicated, but there is precious metal, you can begin to review the functioning process. So, when the ignition is turned on, the platinum wire begins to heat up. It is located clearly in the middle of the plastic tube and is the arm of the main bridge of resistors. In the circuit, the current strength is constantly kept at the same level, due to which the temperature is stable. You press on the gas pedal, the throttle valve opens and air is drawn into the fuel system. The flow cools the wire, and the resistance of the platinum drops.

The control system notices the temperature change and increases the voltage to heat the wire to the desired value. Only after the temperature has stabilized will the system come into equilibrium. At this moment, the resistance of the platinum wiring and its temperature will have an optimal ratio. It is worth noting that the current that flows through the measuring wire varies from 500 to 1200 μA. It also flows in the calibration resistor circuit, which sends a signal to the control unit. The latter, having received the data, calculates the required amount of gasoline according to the fuel map.

Carrying out maintenance

The sensor does not require any maintenance as such. Measures to clean the system are taken by the electronic control unit. And if the air flow sensor, the signs of malfunction of which will be discussed below, is broken, then a lot of dirt and dust will accumulate in it. The air entering the tube cannot be completely cleaned by any filter. Therefore, a method is provided by which all the dirt that accumulates on the platinum wire literally evaporates. There is a small peculiarity in the operating algorithm of the electronic control unit.

When you turn off the engine, a voltage is applied to the platinum wire that can heat it up to 1000 degrees. The heating occurs within a second, this time is enough to get rid of all the accumulated dirt on the surface of the wire. If you decide to restore the sensor yourself, you will need to thoroughly clean the wire and mesh. When carrying out work, it is forbidden to touch these objects, otherwise you will only have to change the entire device; it will not be able to work normally.

Disadvantages of the air flow sensor

Despite all the words said above about the simplicity of design and operation, the device has many disadvantages. The most important thing: it cannot be repaired. It’s unlikely that anyone will want to spend 2,000 rubles on a new one. It is, of course, possible to clean the sensor, but this should only be done if you have the appropriate qualifications and experience. And if the wire is damaged or even torn off, you should not even try to revive the sensor.

Among the disadvantages is that it does not measure air mass. It monitors the volume that has passed through it. This complicates the entire system, since it is necessary to know the air density to calculate the mass. For this purpose, a sensor is provided that measures temperature. Without measuring this parameter, it is impossible to calculate the mass. Modern designers have tried to move away from the classic MAF design and conducted tests with pressure sensors. As a result, the Nissan air flow sensor from the early 2000s began to measure air pressure rather than volume.

Symptoms of a problem

The first sign that will immediately catch your eye is the illuminated CHECK ENGINE light on the instrument panel. Unfortunately, it talks about all engine breakdowns, so there are two options for determining an accurate diagnosis - visit a service station or monitor the condition of the engine in different operating modes. The second one turns out to be cheaper, but there is not much chance of determining which component in the engine is acting up. The symptoms of many breakdowns are the same. So, the engine can “triple” both due to malfunctions in the ignition system and when there is a breakdown in the fuel mechanism. Therefore, it is better to spend money, but send the car to a diagnostician who will tell you exactly which element has failed.

An increase or decrease in idle speed clearly indicates that there is a malfunction in the fuel supply system. In particular, such symptoms are also characteristic of defects in the air flow sensor. When accelerating, the car “thinks” for a long time, the speed is gained extremely slowly. The idle speed not only changes, but also becomes unstable. And this is only if the engine was able to start at all. Often it does not respond at all when the starter rotates. Here's how to check your air flow sensor by looking at the external signs only. But an accurate diagnosis can be made only after complete disassembly of the device.

Replace or repair?

When the sensor breaks down, the following question immediately arises. But you need to immediately decide whether there is a malfunction in the device itself? Breaks and defects of active elements are extremely rare, but contamination is a popular cause of failure. There is a violation of the integrity of the corrugated hose that connects the sensor and the throttle. The presence of cracks on it causes CHECK ENGINE to light up and the engine simply stops working.

Therefore, you need to make sure that the fault lies in the sensor. If contamination occurs, it can be removed with a special spray. These are sold in stores for cleaning the throttle body. Please note that wiping the inner surface with your fingers or a cloth is prohibited. Only contactless cleaning is allowed.

Conclusion

To avoid expensive repairs, because even the VAZ-2110 air flow sensor costs a decent amount - about 2,000 rubles depending on the manufacturer, carefully monitor the condition of your car. Timely replacement of the air filter is a guarantee of stable and trouble-free operation of the air flow sensor on any car. You also need to pay due attention to the condition of the piston group. If oil begins to be thrown into the throttle assembly, then destruction of the mass air flow sensor is inevitable.

The mass air flow sensor DMRV is one of the main ones in the engine management system. It informs the engine control unit about the mass amount of air entering the intake manifold, and therefore oxygen, to form the fuel mixture in the required proportions.

A malfunctioning mass air flow sensor leads to an incorrect oxygen-fuel ratio in the mixture, which causes problems in engine operation.

What is a mass air flow sensor in a car and where is it located?

The mass air flow sensor in most cars is located in the pipe after the air filter. The air supplied there is already purified from dust and foreign hard and soft impurities. Contamination of the DMV leads to its failure. Therefore, it is important to change the car air filter on time.

In some cars, the MAF fasteners are located symmetrically; the sensor can be installed in different directions. In order not to confuse the direction of installation of the sensor, an arrow in the direction of air movement is marked on it.

Principle of operation

Cars up until the 1980s used vane-type sensors. In appearance they resembled a throttle valve. The air moving through the pipe rotated the blade(s) of the mass flow sensor, which were on the same shaft with a variable resistor. A reference voltage was applied to the resistor. Data about the change in voltage at the middle terminal of the variable resistor was transmitted to the control unit.

Owners of BMW 3 Series cars from the 1980s remember how much trouble the incorrect operation of the blade-type mass air flow sensor caused.

It is much easier to record the movement of air in the pipe by pressure. It is known from the laws of physics that as the speed of movement of air masses in the pipe increases, the pressure decreases.

Some manufacturers installed volumetric air consumption sensors as recorders. However, their data does not correspond to the quantitative oxygen content in the air.

It is known that as temperature increases, air density decreases. The mass amount of oxygen in a certain volume (density) also decreases.

By the way, this is why some diesel cars are equipped with an intercooler to reduce the intake air temperature, thereby enriching the mixture with oxygen and increasing power.

In the 90s, anemometer-type mass air flow sensors began to be installed on cars.

In general, the sensor consists of two devices: a temperature sensor and a heating filament made of refractory material. The principle of operation of the mass air flow sensor is simple.

The current coming from the engine control unit heats the filament to a certain temperature, which is recorded by the temperature sensor built into the mass air flow sensor. While the car is moving, when the accelerator pedal is pressed, the speed of air movement in the pipe increases, and it cools the thread.

The control unit increases the current to achieve maintaining the temperature of the heated filament at a stable level. Thus, the control unit receives information about the quantitative air consumption based on the current of the heated filament. Sometimes a very thin plate is used as a thread.

Some manufacturers claim that the heating element (filament or plate) is made of platinum. Judging by the cost of the original mass air flow sensors, this can be believed.

Some engine control unit circuits provide a “fire-up” mode for the mass air flow sensor after stopping the engine. In this case, a large current is supplied to the filament, heating it to a temperature of about 1000 degrees Celsius. Thus, the thread (plate) self-cleanses from various oils and dirt that may get on it while the car is moving.

Signs of a DMRV malfunction

Symptoms of a malfunctioning mass air flow sensor:

• unstable engine operation;
• power failures when pressing the accelerator pedal;
• unstable engine starting (especially in diesel cars);
• “swimming” of engine speed.

If the air flow sensor is faulty, some cars will not start at all. Experienced car enthusiasts know: if there is a suspicion that the mass air flow sensor is not working correctly, you can simply disconnect it from the engine control unit (remove the connector from it).

Video - symptoms of a malfunction of the mass air flow sensor:

In many cases, after this the car starts and runs stably. This happens because the engine control unit goes into emergency mode and, when forming the quality of the mixture, is guided not by the mass air flow sensor data, but by data on the throttle position.

How to check the mass air flow sensor

The most reliable method of checking the mass air flow sensor is to “throw in” a known-good sensor. It is better to take it from the owner of a similar car.

Be careful! During the dismantling and installation process, there is a fear of damage to the mass air flow sensor.

It contains very thin threads (plates) that are easily damaged. It is not recommended to take a used sensor for disassembly; with a high degree of probability it may not work. A malfunction of the sensor can cause even slight contamination or coating with an oil coating.

The second method is to disconnect the connector from the mass air flow sensor. If the car starts and the engine runs smoothly and picks up speed smoothly, this is evidence of a possible sensor malfunction.

Checking the mass air flow sensor with a multimeter

You can check the serviceability of the threads (plates) using a multimeter. To do this, you need to know the sensor circuit and pinout. For example, in VAZ cars it is necessary to connect the multimeter probes (with the connector turned on) between the green and yellow wires of the connector.

This can be done using sewing needles, pins, piercing the insulation or inserting them into the connector on the other side. A voltage from 1.0 to 1.1 Volts will indicate that the sensor is working, more than 1.2 Volts - the sensor must be replaced.

Video - checking the mass air flow sensor with a multimeter:

Some mass air flow sensors can be checked visually. They have two threads (plates). If you remove the sensor, you can visually assess their integrity and the absence of contamination.

There are more complex control methods using a hair dryer to simulate the movement of air flows, an oscilloscope, but they are not as effective.

Broken sensor threads, lack of voltages and currents of the mass flow sensor are determined by diagnostic devices. In cars produced after 2005, it provides information about the mass consumption of the fuel mixture, which can also be used to judge the performance of the mass air flow sensor.

How to clean the air flow sensor

Some car enthusiasts believe that cleaning sensors is a way to extend their operating time. For the mass air flow sensor, it’s rather the opposite (!).

Under no circumstances should you even touch its working areas, let alone clean it.

The only way to remove contaminants is by washing, and not in aggressive liquids. It is better to take a mild solvent (for example, 646) or a carburetor cleaner.

Video - how to clean and check the mass air flow sensor on a Ssang Yong Kyron:

Carefully immerse the sensor in the solvent, hold it in it for about twenty minutes, and carefully remove it. Do not dangle the liquid as this may damage the thin thread.

To dry the sensor, you can use a regular hair dryer.

Replacing the air flow meter

When replacing the mass air flow sensor, carefully remove the old sensor. Perhaps it is still operational, and the problem of engine malfunction is not in it.

It is better to carry out installation and dismantling in a warm room; in this case, the pipes will be softer and you will not have to use additional effort.

When installing a new mass air flow sensor, extreme care should be taken to avoid damaging sensitive sensors. Try not to place the sensor on the table; immediately after removing it from the package, install it in its normal place in the pipe.