What is the phenomenon that the air flowmeter is broken?
What is the phenomenon that the air flowmeter is broken?
Air flowmeter signal is the core data of engine electronic control system. Once the sensor fails, it will have a great impact on the normal work of the engine, the fault indicator light of the car will light up, and the engine will appear idle jitter, poor acceleration, flameout after starting and so on. Due to/
air metre
With the development of China's industry, many changes have taken place in the types of air flow meters. According to the development of the times, air flow meters can be divided into four types: L type, D type, hot wire type and hot film type. The first generation L-type air flowmeter has the simplest structure. Of course, there are no models in use now. The second type is the D-type air flowmeter, which is an upgraded version of the first generation air flowmeter and can improve the performance of the air flowmeter.
The third type is the widely used hot-wire air flowmeter. The biggest feature is to keep the temperature of the hot wire constant by using the characteristics of thermistor, so as to keep the accuracy of measuring the intake air volume stable. The structure and working principle of hot-film air flowmeter are similar to that of hot-wire flowmeter, mainly to improve the shortcoming that hot-wire flowmeter will get dirty after long-term use (which will make the measured value inaccurate), and it is the most widely used flowmeter at present.
The structure of the air flowmeter is shown in the following figure. Inside the gas flowmeter is a Whiston bridge composed of thermistor, platinum hot wire and two precision resistors. Engine ECU mentioned supplying current to the power transistor to heat the platinum hot wire to a certain temperature. When air flows through the temperature sensor and the platinum hot wire, it will take away the heat of the platinum hot wire. At this time, the electronic control unit will increase the voltage flowing through the Wheatstone bridge, which is proportional to the air intake through the intake pipe. The ECU will use this value to calculate the fuel injection quantity, thus changing the air-fuel ratio.
Cause of failure of air flowmeter
Various faults will occur during the use of the air flowmeter, which will affect the normal use of the air flowmeter. The air flow meter has the following main reasons:
1. air flowmeter line fault
During the normal operation of the engine control system, the data provided by all sensors must be correct and reliable. When the pipeline liquid level of the sensor fails, resulting in the output signal exceeding the normal value within the specified range, the engine electronic control unit can not recognize the signal normally. For example, if the maximum voltage output by the sensor is 5V, then the ECU can't correctly know what the information transmitted by the sensor is. The ECU will store the fault information in the memory and output the fault code at the same time.
The output voltage of the air flow meter is between 0.2 and 4.9V. When the voltage signal received by the ECU exceeds this range for many times, it will report the relevant fault code, but the engine ECU will occasionally not notice the voltage abnormality, which may be caused by accidental contact of lines or vehicle bumps during driving.
If the fault code of P0 100 is output, the sensor line is short-circuited or open-circuited; If it is P0 102, the sensor circuit is open; If it is P0 103, the sensor line is short-circuited. It should be noted that if the sensor fails, check the wiring first, and then check whether the sensor itself is damaged.
2. Dirty throttle causes sensor failure.
This kind of fault mainly occurs in the hot-wire air flowmeter, because this type of air flowmeter is installed in front of the throttle, usually used to provide the vacuum pressure required by the engine, and is connected with many vacuum tubes, which will leave the throttle empty after long-term use.
After the hot wire of air mass flowmeter is fouled, the heat transfer performance becomes worse, which leads to the low signal transmitted to ECU when the air volume is large, the fuel supply is low and the concentration of lean mixture is low, which leads to the poor idle speed of the engine and the phenomenon of "backfire" when the engine accelerates rapidly.
Fault phenomenon of air flowmeter
1. The failure of the air flow meter caused the engine to trip and shut down intermittently.
When this happens, the idle speed of the vehicle is normal, the in-situ acceleration is normal, and it is normal to drive at the usual speed. However, when the vehicle speed exceeds 120km/h, the above fault may occur, which may be caused by the inaccurate signal output of the air flowmeter at high speed.
There are many possible reasons for the high-speed stall of the engine, such as reduced fuel injection, ignition system failure, exhaust gas recirculation, fuel vapor recovery system of gasoline, incorrect sensor output signal, etc. At this point, we can use an oscilloscope to connect the output end of the air flowmeter for trial operation to see if the rectangular signal output is interrupted occasionally when the fault occurs.
2. The fault of the air flow meter causes the engine to emit black smoke, resulting in high fuel consumption.
The engine emits black smoke, and the fuel consumption is high, which indicates that the fuel injection quantity of the fuel injector is large and the engine mixture is too rich. The air flow meter affects the fuel injection, so it will also cause this fault. Under the condition that the intake of the engine is stable (no air leakage), the signal fluctuation of the air flowmeter should be stable. If the frequency of the signal output by the flowmeter is wrong, for example, when idling, it should be 30-40Hz and changed to 500Hz, then the corresponding fuel injection amount at this time is 8ms (normal idling is 2-3ms), indicating that there is more fuel in the mixture.
Air flowmeter is an important sensor of electronically controlled engine. The quality of this sensor will affect the fault state of the engine, such as engine flameout, operation, black smoke and high fuel consumption. The main reason for the damage of the air flowmeter is the line fault or the air flowmeter is too dirty.
How often do you change the air filter and air conditioner filter? Generally, the air filter and air conditioning filter element can be replaced every 10000 km or so. Simply put, it can be changed every maintenance. It is not recommended to blow these two kinds of filter elements with a ram. A filter element is a consumable, which is cheap, so you don't have to save it here. Secondly, the high-pressure air duct can easily affect the surface structure of the filter element, making the filter element lose its filtering ability, which may bring trouble to the vehicle!
Adjust the filter element first when it is empty. The empty filter element is called empty by filtration, so even if it is never replaced, it will not cause harm to the vehicle, which will only lead to poor air quality inside the vehicle. Therefore, it is not necessary to replace the empty filter element regularly. I feel that the air quality inside the car is not good or there is an odor that can be replaced. Empty filter elements are usually in the first mate's handcuff box. It is difficult for you to blow the old filter cartridge with the air duct, because the empty filter cartridge is in a wet state and may rot after being used for a period of time. At this time, blowing the high-pressure air duct will not form an empty filter element at all, and only the empty filter element can be replaced.
Service life of air filter element
Many friends have the habit of cleaning the air filter regularly. For example, before the maintenance time, take a high-pressure air duct from the garage in advance and blow it hard at the air filter. Of course, this operation can really clean the floating dust on the surface, but only in places that we can't see with the naked eye (such as empty filters)
Filter effect: new empty filter >: old empty filter >: empty filter has been cleaned.
When the vehicle is running normally, the air filters the wind and the contact area is large, so the pressure formed is relatively low, generally between 6-7 kPa. The opening of the high-pressure air duct in the garage is small, but the pressure is great. Such a small opening, blowing into the air filter element, the windward pressure can reach 3 or 4 kPa, such a high pressure. The pores on the surface of the filter paper will be completely enlarged by the sudden increase of pressure, thus losing the filtering ability, and the silica particles attached to the surface are extremely difficult to be blown off and even forced to enter the pores!
In short, after such operation, the air filter element basically loses its ability to filter air and block particles. Although it is clean on the surface, it is only a psychological comfort! I have seen a test before. There are three samples, a brand-new air filter element, an air filter element of 20,000-40,000 km, and a filter element of 30,000 km//kloc-0,000 km, but it has been cleaned by the air duct. In the subsequent filter test, 40000km empty filter and brand-new /[/k0] filter were found.
Therefore, the filter element of an empty air cleaner is either replaced with a new filter element or not moved. The filtering effect of the old filter element covered with floating ash is also better than that of the clean filter element with clean surface. The surface of the filter element blown out of the air duct is clean, and the filtering ability is actually greatly reduced, which is just psychological comfort. And the air conditioning of the filter element is related to our health. After all, the quality of air conditioning filter is closely related to the air quality inside the car. There is no problem in adjusting the filter ring frequently, and there is no harm in replacing it in advance. Empty in a damp environment to adjust the filter element.
What happened to the air flowmeter @20 19?