(abbreviated as DFID) is an indispensable device that determines and regulates the supply of the required amount of air into the combustion chamber of the internal combustion engine. Its design necessarily includes a hot-wire anemometer, the main function of which is to measure the flow rate of the supplied gases. Sensor 2115 is located near the air filter. But regardless of its location, it breaks the same way, like everyone else’s. modern models Volzhsky plant. In this article we will look at and also find out how to check its current condition without calling specialists.

How can you determine that the mass air flow sensor needs to be replaced or repaired?

In fact, there are a lot of symptoms of breakdowns of this part. The main symptom of a sensor malfunction mass flow air - this is the appearance of a Check Engine lamp on the dashboard (literally - “Check the engine”). Also, a malfunction of the mass air flow sensor may be indicated by an increased Another symptom is poor engine starting. This problem may occur even when the charge level battery equal to 80-99%, and it’s 30 o C hot outside. Strange movement of the car can also signal a breakdown.

The main sign of a malfunction of the mass air flow sensor may be poor acceleration dynamics and “dips” in movement, that is, the car brakes sharply and then accelerates sharply. And the last symptom is poor engine performance. If the engine constantly runs intermittently, and its speed constantly “jumps”, this is a sign of a malfunction of the mass air flow sensor.

Determine the current state of the part

This way you can reduce air consumption without going to a service station; this instruction will be useful to all car enthusiasts. So, in order to check the mass air flow sensor, you need to unscrew the clamp securing the air intake corrugation at the outlet.

This is done using a shaped screwdriver.

After removing the clamp, carefully remove the pipe and examine its surface. Ideally, its interior should be dry and clean. By the way, if you do not change the air filter in a timely manner, it can negatively affect the condition of the air flow sensor and contaminate it with small particles of road dust. Next, using a 10-mm open-end wrench, unscrew the fastening elements of the mass flow sensor and check its condition. When the rubber seal ring is placed out of place on the inlet edge, it must be corrected or replaced immediately. Otherwise, dust will cause the sensor to stop functioning normally. If, during disassembly, you find traces of oil in the design of the diagnosed part, this indicates a clogged oil sump or an increased concentration of lubricant in the engine. In the first case, the system should be cleaned, and in the second, excess oil should be drained.

Remember, no matter what signs and malfunctions are present, under no circumstances should you neglect replacing or repairing the sensor, otherwise you will be guaranteed increased fuel consumption.

Motor load, condition road surface, vehicle load are one of the few factors that determine engine operating modes internal combustion. The very first and strict rule defining optimal conditions for engine operation, is the correct correspondence of the amount of air to fuel, the standard of which is 14.7 kg of air per 1 liter of gasoline.

The main task of the sensor is to measure the ideal amount of incoming air so that the engine efficiency is as high as possible.

DMVR: what is it?

Mass air flow sensor is a hot-wire type sensor that reads information about the amount of air that enters the intake manifold, which allows the electronic engine management system to calculate the correct fuel-air mixture ratio. This sensor is installed between the air filter housing and the intake manifold, and a corrugation connects them.

DMVR – hot-wire sensor

Before servicing or repairing, it is necessary to understand the design of this sensor.

The air flow sensor consists of 6 parts:

1. 1. Pay.
2. 2. Frame.
3. 3. Radiator.
4. 4. Sensor (sensitive element).
5. 5. Pipe branch.
6. 6. Inlet and outlet screens.

The main part of the mass air flow sensor is a nickel network or wire (sensitive element), to which a current is supplied that heats the filament. The average temperature of the threads is 75-100 degrees or higher than the temperature of the air passing by the sensor.

How to check the mass air flow sensor with a multimeter and other methods

Immediately before checking the malfunction, you should understand the symptoms. 5 of these have been identified:

1. 1. The Check Engine lights up on the instrument panel (indicating some kind of engine malfunction).
2. 2. A sharp increase in gasoline consumption.
3. 3. Late response to the gas pedal, dynamics decreases.
4. 4. At operating temperature the engine does not start.
5. 5. Loss of power.

The question arises: is it possible to drive when a malfunction of the mass air flow sensor is detected?

When the sensor is disconnected from the power supply, the engine begins to operate in emergency mode. The fuel to air ratio now depends on the throttle opening angle, which increases gas mileage. The minimum crankshaft speed starts at 1500 rpm.

There are 5 ways to check the operation of the sensor.

Method No. 1: disconnect power from the mass air flow sensor

It is necessary to remove the connector from the sensor and start the engine. In this case, the “Check Engine” should light up, the minimum speed will increase to 1500 rpm. If you feel the speed of a car without a sensor, then this is a direct sign of a non-functioning air flow sensor.

Method No. 2: Reflashing the control unit.

In case the firmware of the “brains” was previously carried out, then it is impossible to know how the engine is programmed for an emergency in the first method. It is necessary to take a plate 1 mm thick and place it under the damper stop. The engine speed should increase. Then you need to remove the connector from the sensor. If the engine does not stall, it means that the problem lies in the firmware of the control unit, namely with the idle speed controller without a mass air flow sensor in emergency mode.

Method No. 3: Checking the sensor using a multimeter

This method does not work on all mass air flow sensors. You need to set the tester to measure direct current and put a maximum of 2 V.

There are 4 wires suitable for the sensor, each marked with its own color, starting from the closest to windshield:

1. The yellow wire is responsible for the input of the air flow sensor signal.
2. Gray wire (white) – supply voltage output channel.
3. Green wire – ground.
4. Black wire (with a pink stripe) is responsible for the output to the main relay.

The colors on the mass flow sensor may be different, but the pin layout is the same in all of them.

Next, turn on the ignition, but do not start the engine. Touch the red probe to the first wire (yellow), the black probe to ground (green wire). This method shows the voltage between two wires.

The new sensor voltage should be between 0.99 and 1.01. If the voltage begins to increase over time, this means that the sensor is rapidly wearing out.

Voltage indicators:

– 1,01 – 1,02 V– The air flow sensor is in excellent condition;

– 1,02- 1,03 V- satisfactory condition;

– 1,03 – 1,04 V– the resource of the part is almost exhausted;

– 1,04 – 1,05 Vand higher - the mass air flow sensor needs to be replaced.

Method number 4: inspection of the sensor

It is necessary to remove the mass air flow sensor from the seat by disconnecting it from the air filter housing and bellows. The inner surface of the sensor must be dry, without traces of condensation and oil. Frequent sensor failure occurs because the air filter is rarely changed, dirt gets on the sensitive element, and it gives erroneous readings. The presence of oil in the sensor indicates an increased oil level in the engine or clogging of the crankcase ventilation.

Next, you need to make sure that the sealing ring on the seat where the corrugation fits is not stuck on the air filter housing. If this happens, then air leaks from the seat, which pulls dust with it, which causes rapid wear of the sensor.

Method No. 5: installation of a similar sensor.

If it is possible to take the same mass air flow sensor, then using an example of its operation you can draw conclusions about the performance of your sensor.

What are the dangers of malfunctions?

1. Increased gasoline consumption.
2. Unstable engine operation.
3. The engine will not operate at temperatures above 90 degrees.

Troubleshooting

The peculiarity of the air flow sensor is that it is maintenance-free and cannot be repaired. It is only allowed to be cleaned. It is strictly forbidden to blow the sensor with compressed air, clean it with ether, acetone, swabs and cotton swabs, as these operations can damage the sensitive element. There are special “Flow meter cleaner” flushes that extend the service life of the part, provided that its voltage does not exceed 1.13V.

Is it possible to installsensor from another car brand

Flow meters are manufactured specifically for each engine, as a result of which they also have different output voltages. If a foreign sensor is installed, the engine control unit will not be able to properly process the sent signals, which will affect the stability of the engine.

If there is no other way out, then the ECU can be flashed for someone else’s flow meter, provided that this operation is carried out by a specialist.

Video: how to check the DMRV with a multimeter

Bottom line

The mass air flow sensor is an integral part of the intake and fuel system, which indicates how much fuel to deliver at a certain moment. Its malfunction can have a detrimental effect on the operation of the motor. In order to maximize the life of the sensor, it is necessary first of all to monitor the parts that are directly related to it (the condition of the air filter, the oil level and the condition of crankcase gas suction clogging). Average service life of mass air flow sensor at proper care may be over 50,000 km or two years.

For optimal operation of an injection internal combustion engine (hereinafter referred to as ICE), it is necessary to take into account how much air mixture enters the combustion chambers of the cylinders. Based on these data, the electronic control unit (hereinafter referred to as the ECU) determines the fuel supply conditions. In addition to information from the mass air flow sensor, its pressure and temperature are taken into account. Since mass air flow sensors are the most significant, we will consider their types, design features, diagnostic and replacement capabilities.

Purpose and explanation of the abbreviation

Flow meters, also known as volume meters or mass air flow meters (not to be confused with mass air flow meters and mass air flow sensors), are installed in diesel or gasoline-powered vehicles. The location of this sensor is not difficult to find, since it controls the air supply, you should look for it in the corresponding system, namely, after the air filter, on the way to the throttle valve (DZ).

The device is connected to the engine control unit. In cases where the mass air flow sensor is in a faulty condition or is missing, a rough calculation can be made based on the position of the air flow sensor. But with this measurement method it is impossible to ensure high accuracy, which will immediately lead to excessive fuel consumption. This once again indicates the key role of the flow meter in calculating the fuel mass supplied through the injectors.

In addition to information from the mass air flow sensor, the control unit also processes data coming from the following devices: camshaft sensor (camshaft sensor), DD (knock meter), remote sensor, cooling system temperature sensor, acidity meter (lambda probe), etc.

Types of mass air flow sensors, their design features and operating principle

Three types of VU meters are most widespread:

• Wire or thread.
• Film.
• Volumetric.

In the first two, the operating principle is based on obtaining information about the mass of the air flow by measuring its temperature. The latter may involve two accounting options:

Vortex sensor design (widely used by Mitsubishi Motors)

Designations:

• A – pressure measurement sensor to record the passage of the vortex. That is, the frequency of pressure and vortex formation will be the same, which makes it possible to measure the flow of the air mixture. At the output, using an ADC, the analog signal is converted into a digital one and transmitted to the ECU.
• B - special tubes that form an air flow similar in properties to laminar.
• C – bypass air ducts.
• D – column with sharp edges on which Karman vortices are formed.
• E – holes used to measure pressure.
• F – direction of air flow.

Wire sensors

Until recently, the thread mass air flow sensor was the most common type of sensor installed on domestic cars model range GAZ and VAZ. An example of a wire flow meter design is shown below.

Designations:

• A – Electronic board.
• B – Connector for connecting the mass air flow sensor to the computer.
• C – CO adjustment.
• D – Flow meter housing.
• E – Ring.
• F – Platinum wire.
• G – Resistor for temperature compensation.
• N – Ring holder.
• I – Electronic board casing.

Operating principle and example of a functional diagram of a filament VU meter.

Having understood the design of the device, let's move on to the principle of its operation, it is based on the hot-wire method, in which a thermistor (RT), heated by the current passing through it, is placed in the air flow. Under its influence, the heat transfer changes, and, accordingly, the resistance RT, which makes it possible to calculate the volumetric flow rate of the air mixture? using King's equation:

I 2 *R=(K 1 +K 2 * ⎷ Q )*(T 1 -T 2) ,

where I is the current passing through RT and heating it to temperature T1. In this case, T 2 is the temperature environment, and K 1 and K 2 are constant coefficients.

Based on the above formula, you can derive the volumetric air flow rate:

Q = (1/K 2)*(I 2 *R T /(T 1 – T 2) – K 1)

An example of a functional diagram with bridge connection of thermoelements is shown below.

Designations:

• Q - measured air flow.
• U – signal amplifier.
• R T - wire thermal resistance, as a rule, is made of platinum or tungsten filament, the thickness of which is in the range of 5.0-20.0 microns.
• R R – temperature compensator.
• R 1 -R 3 – ordinary resistances.

When the flow velocity is close to zero, the RT is heated to a certain temperature by the current passing through it, which allows the bridge to be kept in equilibrium. As soon as the flow of the air mixture increases, the thermistor begins to cool, which leads to a change in its internal resistance, and, as a result, an imbalance in the bridge circuit. As a result of this process, a current is generated at the output of the amplifier unit, which partially passes through the temperature compensator, which leads to the release of heat and makes it possible to compensate for its loss from the flow of the air mixture and restores the balance of the bridge.

The described process allows you to calculate the flow rate of the air mixture based on the amount of current passing through the bridge. In order for the signal to be perceived by the ECU, it is converted into a digital or analog format. The first allows you to determine the flow rate by the frequency of the output voltage, the second - by its level.

This implementation has significant drawback– high temperature error, so many manufacturers add a thermistor similar to the main one to the design, but do not expose it to air flow.

During operation, dust or dirt deposits may accumulate on the wire thermistor; to prevent this, this element is subjected to short-term high-temperature heating. It is performed after the internal combustion engine is turned off.

Film air meters

A film MAF works on the same principle as a filament one. The main differences lie in the design. In particular, silicon crystal is used instead of platinum filament resistance wire. It is coated with several layers of platinum plating, each of which plays a specific functional role, namely:

• Temperature sensor.
• Thermal resistances (usually there are two of them).
• Heating (compensation) resistor.

This crystal is installed in a protective casing and placed in a special channel through which the air mixture passes. The geometry of the channel is designed in such a way that temperature measurements are taken not only from the input flow, but also from the reflected one. Thanks to the created conditions, it is achieved high speed movement of the air mixture, which does not contribute to the deposition of dust or dirt on the protective housing of the crystal.

Designations:

• A – Flow meter body into which the measuring device (E) is inserted.
• B – Contacts of the connector that connects to the ECU.
• C – Sensitive element (silicon crystal with several layers of coating, placed in a protective casing).
• D – Electronic controller, with the help of which preliminary processing of signals is carried out.
• E – Body of the measuring device.
• F – Channel configured to capture thermal indicators from the reflected and input stream.
• G – Measured flow of air mixture.

As mentioned above, the operating principles of filament and film sensors are similar. That is, the sensitive element is initially heated to temperature. The flow of the air mixture cools the thermoelement, which makes it possible to calculate the mass of the air mixture passing through the sensor.

As in filament devices, the output signal can be analog or converted to digital format using an ADC.

It should be noted that the error of filament VU meters is about 1%; for film analogues this parameter is about 4%. However, most manufacturers have switched to film sensors. This is explained both by the lower cost of the latter and by the expanded functionality of the ECUs that process information from these devices. These factors overshadowed the accuracy of the instruments and their speed.

It should be noted that thanks to the development of flash microcontroller manufacturing technology, as well as the introduction of new solutions, it was possible to significantly reduce the error and increase the performance of film structures.

Interchangeability

This issue is quite relevant, especially taking into account the cost of original products from the imported automobile industry. But it’s not so simple here; let’s give an example. In the first production models of the Gorky Automobile Plant, the injection Volgas were equipped with a BOSCH air flow sensor. Somewhat later, imported sensors and controllers replaced domestic products.

A – imported filament air flow sensor manufactured by Bosh (pbt-gf30) and its domestic analogues B – JSCB “Impuls” and C – APZ

Structurally, these products were practically no different, with the exception of a few design features, namely:

• The diameter of the wire used in a wirewound thermistor. Bosch products have a diameter of 0.07 mm, and domestic products have a diameter of 0.10 mm.
• The method of fastening the wire differs in the type of welding. For imported sensors this is resistance welding, for domestic products it is laser welding.
• Shape of a thread thermistor. Bosh has a U-shaped geometry, APZ produces devices with a V-shaped thread, and products from JSC Impulse are distinguished by the square shape of the thread suspension.

All the sensors given as an example were interchangeable until the Gorky Automobile Plant switched to film analogues. The reasons for the transition were described above.

Film air flow sensor Siemens for GAZ 31105

It makes no sense to give a domestic analogue to the sensor shown in the figure, since outwardly it is practically no different.

It should be noted that when switching from filament devices to film ones, most likely, you will need to change the entire system, namely: the sensor itself, the connecting wire from it to the ECU, and, in fact, the controller itself. In some cases, the control can be adapted (reflashed) to work with another sensor. This problem is due to the fact that most filament flowmeters send analog signals, while film flowmeters send digital signals.

It should be noted that the first production VAZ cars with an injection engine were equipped with a filament air flow sensor (made by GM) with a digital output; examples include models 2107, 2109, 2110, etc. Now they are equipped with air flow sensor BOSCH 0 280 218 004 .

To select analogues, you can use information from official sources or thematic forums. As an example, below is a table of the interchangeability of mass air flow sensors for VAZ cars.

The presented table clearly shows that, for example, the MAF sensor 0-280-218-116 is compatible with VAZ 21124 and 21214 engines, but is not suitable for 2114, 2112 (including those with 16 valves). Accordingly, you can find information on other VAZ models (for example, Lada Granta, Kalina, Priora, 21099, 2115, Niva Chevrolet, etc.).

As a rule, there will be no problems with other brands of cars of domestic or joint production (UAZ Patriot ZMZ 409, Daewoo Lanos or Nexia), choosing a replacement mass air flow sensor for them will not be a problem, the same applies to products of the Chinese automobile industry (KIA Ceed, Spectra, Sportage etc.). But in this case, there is a high probability that the MAF pinout may not match; a soldering iron will help correct the situation.

The situation is much more complicated with European, American and Japanese cars. Therefore, if you have a Toyota, Volkswagen Passat, Subaru, Mercedes, Ford Focus, Nissan Premiere P12, Renault Megane or another European, American or Japanese car, before replacing the mass air flow sensor, you need to carefully weigh all the solution options.

If you are interested, you can search online for an epic about an attempt to replace the “native” air meter with an analogue on a Nissan Almera H16. One attempt resulted in excessive fuel consumption even at idle.

In some cases, searching for an analogue one will be justified, especially if you take into account the cost of the “native” VU meter (for example, the BMW E160 or Nissan X-Trail T30).

Functionality check

Before diagnosing the mass air flow sensor, you need to know the symptoms that allow you to determine the degree of performance of the MAF (abbreviation for the English name of the device) sensor in the car. We list the main symptoms of a malfunction:

• The consumption of the fuel mixture has increased significantly, while at the same time acceleration has slowed down.
• The internal combustion engine idles with jerks. In this case, a decrease or increase in speed may be observed in idle mode.
• The engine does not start. Actually, this reason in itself does not mean that the flow meter in the car is faulty; there may be other reasons.
• A message appears about a problem with the engine (Cheeck Engine)

Example of the "Cheeck Engine" message displayed (marked in green)

These signs indicate possible malfunction To accurately determine the cause of the failure, it is necessary to perform diagnostics. It's easy to do it yourself. Connecting a diagnostic adapter to the ECU (if this option is possible) will help to significantly simplify the task, and then determine the serviceability or malfunction of the sensor using the error code. For example, error p0100 indicates a fault in the flow meter circuit.

But if you need to carry out diagnostics on domestic cars manufactured 10 years ago or more, then checking the mass air flow sensor can be carried out in one of the following ways:

1. Testing while moving.
2. Diagnostics using a multimeter or tester.
3. External inspection of the sensor.
4. Installation of a similar, known-good device.

Let's consider each of the listed methods.

Testing while driving

The easiest way to check is by analyzing the behavior of the internal combustion engine with the MAF sensor disabled. The algorithm of actions is as follows:

• You need to open the hood, turn off the flow meter, close the hood.
• We start the car, and the internal combustion engine goes into emergency mode. Accordingly, a message indicating a problem with the engine will appear on the dashboard (see Fig. 10). The amount of fuel mixture supplied will depend on the position of the remote control.
• Check the dynamics of the car and compare it with what it was before the sensor was turned off. If the car has become more dynamic and power has also increased, then this most likely indicates that the mass air flow sensor is faulty.

Note that you can continue driving with the device turned off, but this is highly not recommended. Firstly, the consumption of the fuel mixture increases, and secondly, the lack of control over the oxygen regulator leads to increased pollution.

Diagnostics using a multimeter or tester

Signs of a malfunction of the mass air flow sensor can be identified by connecting the black probe to ground, and the red probe to the sensor signal input (the pinout can be found in the device data sheet, the main parameters are also indicated there).

Next, we set the measurement limits to 2.0 V, turn on the ignition and take measurements. If the device does not display anything, you need to check that the probes are connected correctly to ground and the flow meter signal. Based on the readings of the device, you can judge the general condition of the device:

• A voltage of 0.99-1.01 V indicates that the sensor is new and working properly.
• 1.01-1.02 V – used device, but its condition is good.
• 1.02-1.03 V - indicates that the device is still operational.
• 1.03 -1.04 the condition is approaching critical, that is, in the near future it is necessary to replace the mass air flow sensor with a new sensor.
• 1.04-1.05 – the device’s resources are almost exhausted.
• Over 1.05 - a new mass air flow sensor is definitely needed.

That is, you can correctly judge the state of the sensor by the voltage, low level signal indicates a working condition.

External inspection of the sensor

This diagnostic method is no less effective than the previous ones. All that is necessary is to remove the sensor and assess its condition.

Inspect the sensor for damage and fluid

Characteristic signs of a malfunction are mechanical damage and liquid in the device. The latter indicates that the oil supply system to the engine is not adjusted. If the sensor is very dirty, the air filter should be replaced or cleaned.

Installing a similar, known-good device

This method almost always gives a clear answer to the question of the sensor’s performance. This method is quite difficult to implement in practice without purchasing a new device.

Briefly about the renovation

As a rule, MAF sensors that have become unusable cannot be repaired, except in cases where they require washing and cleaning.

In some cases, it is possible to repair the volumetric air flow sensor board, but this process will not prolong the life of the device for long. As for the boards in film sensors, without special equipment (for example, a programmer for a microcontroller), as well as skills and experience, it is pointless to try to restore them.

Mass air flow sensor is one of the main elements of injection systems of modern cars. Thanks to this sensor, the on-board computer supplies the fuel-air mixture, the engine can operate in optimal mode. Failure of the sensor leads to excessive fuel consumption and a decrease in engine power.

What is a DMRV?

Mass air flow sensor - sensor that measures mass air flow. The device is located in the engine air pipe between the air filter and the throttle valve. Thanks to it, the on-board computer determines the volume of air entering the cylinders necessary for complete combustion of fuel and normal operation of the car.

The device is equipped with a sensitive element consisting of 2 platinum threads with a diameter of 70 microns. One of them is cooled by passing air, and the other is a control. When the ignition is turned on, the wire heats up, sending a signal to the on-board computer to open the throttle valve and cool the element. At the same time, the injectors open, resulting in the formation of the required amount of fuel in a given engine operating mode.

After turning off the engine, the wire heats up to 1000 degrees. As a result, deposits, soot and dust particles on its surface that can affect the sensitivity of the sensor are completely burned.

There are outdated models of mass air flow sensors that operate using a vane damper, as well as more modern modifications with film-silicon elements and platinum coating.

Symptoms of a malfunctioning mass air flow sensor

Usually the sensor breaks due to natural burnout or contamination of the wire surface, which is caused by untimely replacement of the air filter and due to extreme driving. A sensor malfunction can be determined by a number of signs:

• fuel consumption increased;
• the engine is unstable at idle speed;
• the engine does not start;
• The “check” light is on on the on-board computer display.

These symptoms are indirect. Similar phenomena occur when the fuel pump is faulty, the throttle valve is stuck and the USR valve is bent. The exact cause of the breakdown can only be shown by diagnosing the meter using a motor tester, which allows you to construct and evaluate an oscillogram before the cutoff mode or when the ignition is turned on.

How to check the MAF sensor

Checking the mass air flow sensor is not particularly difficult and can be done in several ways:

In move

Considered the simplest, but least effective way sensor diagnostics. Disconnect the connector of the device, start the engine and drive the car, making sure that the engine speed does not fall below 1500. When the air flow meter is turned off, the controller begins to work in emergency mode, forming the fuel mixture according to the throttle position. If this way the car picks up speed faster than with the mass air flow sensor connected, it means the device has failed.

Multimeter

Before checking the mass air flow sensor with a multimeter, turn off the engine and turn the key in the ignition. Connect the red probe to the terminal of the yellow wire (located on the edge of the element, closer to the windshield), and the black probe to the green one (third from the edge).

The colors of the wires may vary, but the location remains the same. The voltage should vary in the range of 0.996...1.01 V, but if the numbers exceed the upper value, then the unit will require immediate replacement. Device readings of 1.05 V or higher indicate a high output voltage and that the sensor is not working.

More detailed instructions checking the DPRV with a multimeter is presented in the video

Visually

Remove the mass air flow sensor by unscrewing the clamp on the corrugated pipeline of the air intake and two screws on the sensor housing. Remove the device from the air filter and inspect its surface - it should be clean, free of traces of oil and dust. The presence of contamination indicates that the platinum threads or film element have failed.

Is it possible to restore the mass air flow sensor?

Only sensors with platinum heat exchangers can be repaired. The surface of the threads is well cleaned of oil, carbon deposits and other contaminants. Film devices are not restored, but replaced with new assembled ones. Before starting work, the mass air flow sensor is carefully disassembled, being careful not to damage the sealing ring. If there is dirt on the membrane or wire, the surface of the elements is washed with WD-40 or medical alcohol.

An excellent option is pure ethyl alcohol, which perfectly cleans platinum elements from any contaminants and evaporates quickly, leaving no traces on the surface. Typically, the wire or cermet is washed for an hour, then left for several hours until completely dry in air. In this case, you must not touch them with your hands or tools to avoid mechanical damage.

The main thing when cleaning the internal parts of the mass air flow sensor is not to break the contacts secured by the gel-like compound. Therefore, during the washing process, it is better not to use compressed air, not to wipe with cotton swabs, or to clean with a knife.

Most organic solvents, which are made on the basis of acetone and esters, are not suitable for cleaning MAFs. Such compositions dissolve the compound, damage the film membrane, and leave an oily film on the surface of the sensitive elements of the unit.

Prevention – effective remedy to extend the service life of the mass air flow sensor. Change the air filter in a timely manner, monitor the condition of the injectors and the oil level in the engine. Then this expensive device will last a long time without breakdowns, and you won’t have to spend money on restoring it.

An air flow meter or mass air flow sensor is a device that measures the amount of air entering the engine cylinders. There are several varieties of them, which differ in the method of measurement. An earlier design is a pitot tube flowmeter (called a vane type). The principle of its operation is based on measuring the deflection of a special plate by the air flow, on the axis of which a potentiometer is installed. The device resembles a throttle valve. Depending on the speed of the air flow, the angle of rotation of the plate changes, and accordingly, the electrical resistance of the potentiometer.

More modern designs flow meters have a hot-wire air flow meter. The principle of its operation is as follows. In the air flow there is a heat exchange element in the form of a platinum wire. The stronger the air flow, the more electricity must be supplied to it in order to maintain a given temperature difference between the wire and the air flowing around it. To remove deposits on a platinum wire (diameter approximately 0.07 mm), a self-cleaning mode is provided, in which, after stopping the engine, which has been running for some time under load, it is briefly heated to a temperature of 1000-1100 ° C.

The most modern flow meters- hot-wire anemometric with a film meter. Their heating and measuring resistors are made in the form of thin platinum layers deposited on the surface of a silicon crystal.

Flow meters with vortex-type meters are also available. The principle of their operation is based on measuring the frequency of vortices that appear at a certain distance behind the protrusion in the wall of the intake channel. It is worth noting that many modern foreign cars use an absolute pressure sensor in the intake manifold instead of an air flow meter.

Types and causes of malfunctions

Each flowmeter design has its own characteristic faults. For “blade” type flowmeters, this is wear of the current-carrying surfaces of the potentiometers and the formation of oily deposits on the working elements. Wear of the potentiometer (“cut” of the current-carrying path) leads to periodic loss of the electrical signal, as a result of which distorted data is transmitted to the control unit. Oily deposits and oxide on the surface of the channel interfere with the movement of the valve (it jams). In the case of hot-wire flowmeters, the cause of the malfunction may be the lack of power supply from the vehicle’s on-board network, as well as unqualified maintenance of this unit. Even attempts to wipe its working surfaces with cotton can damage the flow meter. This unit is not serviceable and cannot be repaired. You can only check the reliability of the contact connections, and in case of contamination, blowing with compressed air or washing the working surfaces with special preparations can help.

Signs of breakdown

Diagnostics

The flow meter is located between the air filter and the throttle valve.

Except external signs During engine operation, a faulty air flow meter can be reported by the built-in diagnostic system. Unfortunately, without diagnostic equipment, it is not always possible to read error codes and determine why the Check Engine warning light is screaming, so you need to contact a service station. You can verify that the air flow meter is faulty by replacing it with a known good one. If the result is an improvement - the reason is in the flow meter, there is no improvement - you need to look in a different direction. Very often to similar external manifestations causes air leaks through connections or cracks in the corrugated hose running from the flow meter to the throttle module.

Repair methods

By bending the plates, you can move the runner to the unworn part of the track.

Most often they simply replace faulty flow meter new. Only flowmeters with a pitot tube (“blade” type) are repairable. Dirt and oily deposits that interfere with the movement of the plate are removed using

aerosols for cleaning the carburetor. Sometimes it is possible to restore the functionality of the potentiometer by moving its board with the contact track or bending the current collector plates so that the contact tip moves along the unworn part of the contact track. Sometimes technicians suggest disconnecting the flow meter from the electronic control unit. But in this case, fuel consumption increases noticeably. Hot-wire flow meters cannot be repaired in a car service center. They are restored only in a repair shop, for example Bosch.

Extending the resource

In order for the air flow meter to last longer, there are two means - change the air filter in a timely manner and monitor the technical condition of the engine (in some old power systems, where the hose of the crankcase gas suction system “cuts in” in front of the air flow meter). Engine repairs can also prevent premature failure of the flow meter, since wear of the piston rings and valve seals leads to an increase in the oil content in the crankcase gases, and this, in turn, causes clogging of the flow meter parts with an oily coating.

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