Symptoms of the defective flow meter + mechanical solutions tuby.me

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1. How does the air flow meter (MAF) work?

The flow meter is a device designed to estimate the amount of air that enters an internal combustion engine.

Most of the debts have two very sensitive heating filaments (thermistors). These filaments are made of platinum or tungsten and are supplied with an electric current to be heated up to a certain temperature. A filament is directly in the line of air and the second is protected from the direct air flow with a screen. When the engine is on, the air flow passes through the sensor and cools the exposed filament more. Consequently, a temperature difference is produced between the thermistors and a higher current for the open filament is needed to restore the required temperature.

Considering the thermistor’s cooling intensity and the difference in reading between the filaments, the electronic control unit (ECU) calculates the amount of air that enters the suction section and determines the demand quantity of fuel for optimal engine operation. Many debtmeter also have an incorporated temperature sensor, for the air that enters the stroke of intake, which increases the accuracy of the readings.

Some Flowmeters models, instead of very sensitive filaments, use a spray ceramic heating element or a semiconductor film, but the operational principle remains the same, as in the following example:

When the flow is close to zero, RT (platinum filament or tungsten thick between 5-20 microns) It is heated to a certain temperature of the current that passes through it, which allows you to keep the bridge in balance. As soon as the flow of the air mixture increases, the thermist begins to cool, which leads to a change in its internal resistance and, consequently, to an imbalance in the circuit of the bridge. The process described allows to calculate the flow of the air mixture, in terms of size of the current that passes through the bridge. In order for ECU to perceive the signal, it is converted into digital or analog form. The first allows you to determine the flow according to the output voltage and the second, based on its level.

This implementation has a significant disadvantage: a high temperature error, so many producers add a thermistor similar to the main design, but does not expose it to the effect of an air flow.

During the operation, dust or dirt deposits can be accumulated on the thermistor of the wire; To prevent this phenomenon, this element is subject to short -term heating at high temperatures.

2. Causes of the failure of an air flow

The most common cause of defect that allows the decimeter is dirt on the heating element: the powder and engine oil distort the readings and cause overheating. The cause of the problems listed above will not necessarily be a defect of the flow meter, they can be determined more precisely only after diagnosis. By yourself you can only inspect the debtor’s connection point (sometimes a defect in the engine operation can occur due to the damage of the air tube). The water, in a short time, can lead to the failure of the air flow meter. For example, when driving at a speed on a torrential rain, the water can go through the air filter and can go directly to the flow meter, producing a specific defect of the flow meter. In addition, the flow meter can be defective quickly due to the losses of the suction system or causes the late replacement of the air filter. It is certain that if sand or the other dirt often penetrate the decimeter, on the road or from the filter, it will not be able to function properly for too long.

In conclusion, the most common causes of flow defect are:

• Poor contact on electrical connections
• Damaged measurement items
• Mechanical damage (vibrations, accidents)
• Movement of measurement items (exit from the measurement frame)

3. Symptoms of the defect of the air flow meter

If the flow meter begins to provide incorrect data, problems occur in the system for preparation for the mixture in the air of fuel, the proportions in the air of fuel are incorrect. Therefore, the following defective symptoms appear:

• The speed of unstable warnings
• The acceleration indicators are violated, the decreases occur to increase speed.
• The difficult or impossible start of the engine
• Abnormal engine running (too large or too small rotation)
• Perceptible deterioration of the dynamics of the vehicle
• Increase in fuel consumption
• The yellow lamp «controls the engine» on board no longer turns off

4. Tips to avoid the defect of the air flow meter and what you need to do

If it broke, the flow meter can no longer be repaired, but is replaced with a new one. Since this is not the cheapest option, it will not be useless to face its maintenance and increase her life.

Tips to avoid the flakes of the flow meter and what is necessary to check periodically:

• The status of the air filter – If the filter is defective or does not meet the technical requirements, the flow meter will seem like a joke compared to the value of the engine repair.
• Motor conditions: oil vapors can enter the air tube when the engine works. The oil deposits that contaminate the platinum element accelerate usury. The condition of the piston rings and the valve gaskets affects the concentration of the engine oil in the casing gases.
• The state of wiring: one of the possible reasons for the discomfort of the flow is the load of electrical contacts. This problem can be solved without serious damage.
• Jack connector control – check the activity for the attachment and correct contact
• Check the measurement elements – the most banal method to check the flow meter (regardless of whether it is defective), consists in dismantling its car and mounting on another car; If that car works with optimal parameters, it means that the flow meter is good and if it does not work it means it is defective.
• Check the aerial decimeter to note certain visible damage. Expert drivers can determine the defect of the Debimeter Maf from its appearance. The first step is to remove the flow meter and then examine it carefully. You can see the penetration of the liquid into the air tube or the presence of mechanical damage. Very often the liquid can reach the sensor for several reasons:
  • Increase in oil level in the tube; In this situation, the oil penetrates the sensor
  • Full oil separator of the ventilation system, the carrier
  • Permanent maintenance of the same air filter, due to which the dirt enters the DMRV thermometer.