In order for the engine to work confidently in all modes, it is necessary that it obtains the optimal composition of the combustible mixture. As you know, the engine alone is not enough fuel, it also needs air. In various modes of engine operation, a different ratio of oxygen and gasoline is required. The air flow meter is responsible for this.
What it is?
This is a mass air flow sensor. It determines the amount of oxygen that is needed to fill the cylinders of an automobile engine under various operating conditions. This device is installed in the intake tract. You can find it after the air filter, in the inlet pipe, or on the housing of the filter element itself.
In operation, the injection system is the main system.
How the device works
This sensor is necessary, as already mentioned, to measure the ideal amount of oxygen that enters the engine. So, DFID calculates the required amount and immediately sends this data to the computer. He calculates the required amount of fuel.
The stronger the driver presses the accelerator pedal, the more air will enter the combustion chamber of the power unit. The flow sensor immediately detects this, and then sends a command to the main computer to send more fuel to the cylinders.
If the car moves uniformly, then in this mode oxygen is consumed in small volumes, which means that fuel consumption will not be large. This air flow meter is monitoring this.
Device, types of sensors, operating principles
Together with technological progress, the design of these devices is also being improved. At the beginning of the development of the automotive industry, a pitot tube was used for these purposes. Also, a similar device was called a blade air flow meter. A thin plate was used as the main element. She was softly fixed. A stream of air bent the plate. A potentiometer, which was also built into the circuit, could measure how much the plate was bent (resistance was measured). This was a signal for the main control unit.
By the same principle, these devices worked on many German cars. So, if you open the BMW air flow meter of the 80s, then there you can find a sensor with just such a device. Naturally, modern cars have systems with a different device.
Among the most modern and common devices on many cars, plate meters are distinguished. In this device, a heat exchanger with two platinum plates is used as a basic element. The plate heats up with electricity.
One plate is working, and the other is a control. The principle of operation of this design is based on the preservation of temperatures on each of the plates, while the temperature should be as uniform as possible. These devices can be found on most cars, this technology is very popular. Only now, instead of membranes, platinum wire is used. The Mercedes air mass meter operates on the same principle.
It works as follows. When the air stream passes through the heat exchanger, it cools the platinum working plate. To maintain the same temperature on this plate as on the control one, a larger current is supplied to it. The change in current is the data that the ECU needs.
Another air mass meter is a device with film meters. The working elements here are platinum plated silicon wafers. This technology is used recently, so these designs are not too common.
There are still devices with vortex meters. Their work is based on measuring the frequencies of vortices, which are created at some distance behind the protrusion in the intake valve.
The most modern design is a membrane type flow meter. It uses a very thin membrane, which is placed in the air stream. On one side and on the other hand, temperature sensors are installed . When the car is moving, the sides cannot cool evenly. The temperature difference is then sent to the computer for further calculations.
In modern foreign cars, such a sensor may even be absent; instead, an absolute pressure system is used.
Symptoms
There is nothing eternal in the car; the air flow meter sensor also fails, moreover, regularly. Many motorists discuss this problem on the forums.
How can you find out that this important device is starting to fail? Very simple. Those indicators that this element measures are very important in the process of proper preparation of a working mixture of fuel and air. Malfunctions of the air flow sensor lead to serious disruptions in the operation of the motor, and even the engine cannot be started at all.
If the flowmeter fails, then the lamp on the dashboard may come on, prompting you to check the engine. Also, malfunctions entail increased fuel consumption, a sharp decline in the power of the power unit. For example, when the Audi air mass meter fails, it is also accompanied by a decrease in the dynamic characteristics of a German car, it becomes very difficult to start the engine, and there is no speed stability in idle mode.
An experienced car enthusiast will say that these are standard signs that may not be associated with DMRV in any way. Yes it is. But the first thing to check for with such symptoms is DMRV.
How to check the air mass meter
Current diagnostic practice involves the use of several verification methods.
The first method is to simply turn off the power to the sensor. To do this, simply disconnect the connector and start the engine. After that, the computer will notify you of serious problems. Fuel will continue to be supplied, but using a
throttle.Next, you need to gain momentum up to 1500, and then it is recommended to go by car. If the unit began to work much faster and more dynamically, it means that the DMRV is to blame for everything.
Diagnostics with a tester
The second method involves the use of a multimeter. Before you begin testing, you must remember that the method is not relevant for all sensors. Only the Bosch air mass meter can be checked with this method.
The first step is to configure the tester at 2 V and put it into constant voltage mode. The Bosch circuitry clearly states that the DMRV should have four wires. So, a signal is sent through the yellow wire, gray-white is the voltage, green is the earth, pink-black is powered along with the main relay.
Now the red probe of the tester must be connected to the yellow wire. The black probe is connected to the green wire. The engine before these measurements must be turned off, but the ignition does not need to be turned off. Next, the voltage is measured.
If the item is operational, then the tester will show 101-102. Permissible indications are 102-103. This is the upper limit at which air flow meter repair is required. If the screen of the tester is 105 or more, then the sensor is broken, replacement is required.
Visual inspection
The third method involves diagnosis only by external signs. In order to visually diagnose a breakdown, you should very carefully examine the internal cavity of the pipe on which the sensor is mounted. This surface should be as clean and dry as possible.
It should be noted that the most common reason why the DMRV is out of order is the commonplace dirt that gets on the work site. This often affects the Audi air mass meter.
To prevent dirt from entering, regularly replace the filters.
In addition, traces of oil can be seen on the surface of the sensor. This indicates that the engine has exceeded the oil norm or there are problems in the crankcase ventilation system.
The next step is to remove the sensor. To perform the dismantling, you will need an open-end wrench. Two bolts are unscrewed and the element is removed from the filter housing for oxygen purification.
At the time of dismantling, make sure that a polyurethane sealant is present. It is often removed with the sensor. A ring is necessary to protect the system from airing. If it is neither in the pipe nor in the sensor, then the reason is the absence of this ring.
If there is no ring, then dirt will enter the part cavity, which is not considered acceptable.
Air flow meter repair
In most cases, these devices are not subject to repair. They are simply replaced with a similar or universal one. Only those that apply the principle of the pitot tube can be repaired. Often there are contaminants that can impede the plate.
You can cope with dirt using special sprays that are used to flush carburetors. In rare cases, you can restore the operation of this variable resistor by installing it on a board with contacts. Sometimes it is possible to cope with this problem by simply bending the plates so that the tip works along the not yet worn part of the site.
Many specialists at the service station offer disconnecting the device from the ECU. However, nothing good will come of it.
Thermoanemometric flow meters are also not amenable to repair. But the Bosch air mass meter can be tried to cure.
How to replace DMRV
If the sensor cannot be repaired, the only way out is to replace it. Replacing the sensor is very simple.
To do this, turn off the ignition, remove the connector. Then, the fastening screws are unscrewed and the inlet hose that is connected to the filter housing is disconnected. Further, the sensor can be safely removed, and instead install a new one. According to this instruction, you can replace any air mass meter. Opel is no exception.
How to extend the resource?
In order for this device to serve faithfully for a longer time, it is necessary to change the air filters in time and constantly monitor the technical condition of the engine. To extend the life of the sensor, you can also repair the engine. Often too worn piston rings and valve seals can lead to premature death of the DMRV.
How to clean DMRV
It is recommended to clean the sensor only when platinum coils are covered with dirt.
It is very important that when cleaning it is forbidden to touch these wires or spirals with your hands. Also, a toothbrush is not suitable for the procedure.
Before checking the air mass meter, it is advisable to remove and thoroughly wash it. Perhaps this will be a simple solution to the problem, since the contacts are often dirty.
The first step is to dismantle the sensor. Then it is disassembled.
When everything is done, that is, spirals are visible, you can sprinkle a little on the spirals using a carburetor cleaner in the form of a spray. If it is new, and there is still high pressure in it, then it is better to spray from a short distance, so the spirals will not be damaged.
As it turned out, the flow meter is a very important sensor, and with proper maintenance it will not often fail.
So, we found out what the mass air flow sensor is intended for.