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Introduction to Common Fault Analysis and Testing of Air Flow Meters - Focus on Microfluidic Control Technology

Introduction to Common Fault Analysis and Testing of Air Flow Meters

Air flow meter common faults are generally divided into hotline breakage, line faults, and hot-wire fouling. Next is a detailed description of common air flow failures.

1. Hotline breakage.
The straight-through air flow meter platinum wire is very thin, and the air flow rate in the intake port changes greatly, and the platinum wire is easy to break; due to maintenance staff not familiar with the flow meter structure principle or the operation is not careful, causing the platinum wire to break Losses also occur from time to time. At this time, because the hot line breaks, the bridge is damaged, and the signal of the flowmeter is lost or mistaken, it will cause difficulties such as engine start-up, idling and stalling, and inability to drive. Some vehicles with self-protection function can start the backup system to make the engine start smoothly. , But the engine speed is limited to about 2000r/min, the car can not move.
To determine if the hot wire (platinum wire) is damaged:
Remove the air filter and intake pipe, start the engine and run it at about 2000r/min for a while, then run it at idle, turn off the ignition switch, and turn off the engine. Observe from the air flow meter inlet whether the hotline heats up after 5 seconds. And for 1s, otherwise the hot line is damaged or the self-cleaning circuit is bad.

2. Line failure.
The connection between the air flow meter and the ECU may be caused by various reasons. Such as poor contact, circuit aging, short circuit or open circuit, etc., some models in the air flow meter signal loss or error, the computer will record the fault code, and enter the fault mode of operation, this time the car can only slow speed, no acceleration, this Faults are also common.

3. Hotline fouling.
Although most of the air flowmeters have self-clearing circuits, due to the poor quality of fuel used in some areas of China, the intake pipe is tempered. Excessive impurities and coke cemented on the metal platinum wire. Long-term driving in the northwest sand area, hotline It is also easy to produce unburnt deposits.
After the hot wire of the air flow meter has fouled, the cooling effect decreases. When the air flow increases, the temperature of the hot wire decreases slowly, and the amount of change in the resistance value also decreases. Therefore, the bridge voltage and the current flowing through it cannot be increased accordingly, so that the signal transmitted to the ECU is low, and the ECU judges that the air flow is small. Therefore, the amount of control injection is also relatively small, so that the mixture is too thin.
Over-leaning of the mixture can cause engine failure, acceleration, weakness, tempering, and lack of power.
Therefore, when the hot line has a lot of fouling, it should be dedusted in time and cleaned with a cleaning product, but it must not be blown with high-pressure air to avoid blowing the platinum wire.

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