Air flow metre also known as the mass air flow sensor, this device is necessary to determine the flow rate of air entering a fuel-injected internal combustion engine. Because air changes its density with temperature and pressure, it’s necessary for the Engine Control Unit-ECU (commonly called The Engine Brain-Box in the country) to balance and deliver the correct fuel mass to the engine for combustion purpose. That’s why when this device gets faulty, it could affect the fuel economy and combustion ratio of a car. And since the engine and transmission functions as one unit in all automatic transmission vehicles, it could also affect the transmission shifting ratio.
Common symptoms of a failing or failed air flow sensor is that it cannot measure the amount of air flow correctly. This causes the engine computer or ECU to miscalculate the amount of injected fuel. As a result, a bad mass air flow sensor causes various drive-ability problems, including a no-start, stalling, lack of power and poor acceleration. In addition, a faulty mass air flow sensor might cause the Check Engine or Service Engine Soon light to come on. Aside from the Check Engine light coming up, it can also alter the shifting pattern of the automatic transmission.
Low mass air flow readings do not mean the sensor is bad. A clogged up air filter or plugged catalytic converter can also cause a lower air flow sensor reading. Vacuum leaks affect the air flow sensor readings too. That’s why mechanics use a working sensor to compare the readings. Sometimes poor electrical connection at the air flow sensor connector could also cause the air flow readings to be out of range. For this reason, the air flow sensor connector terminals as well as the wiring needs to be carefully inspected.
Basic troubleshooting procedure to correct this malfunction, entails first replacing the air filter which is often considered a routine service especially for cars in this part of the world with many untarred roads and cleaning or replacing the air flow sensor itself.
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