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Your Mass Air Flow Sensor (Air Flow Meter) worn out? » Read more about common malfunctions • Repair • Replacement manual
Clean combustion and low consumption thanks to the air flow meter
The air flow meter is an important part of the modern control of internal combustion engines. It ensures clean burning of fuel, protects the catalytic converter and helps save fuel. Air flow meters are also often referred to as mass air flow sensors or air mass sensors.
The task of the air mass sensor
A defined mixture of oxygen and fuel are brought to a controlled explosion in an internal combustion engine. The resulting explosion pressure drives all mechanical parts of the vehicle, all the way to the drive wheels. For the combustion to generate as much pressure as possible, the mixture of oxygen and fuel must be present in an exact proportion. When the combustion chamber receives too little fuel and too much oxygen, this is called a "lean mixture". Performance loss and overheating of the engine are the result. Yet, if too much fuel is burned and too little oxygen, a lot of gasoline or diesel is wasted. Then the resulting combustion is "too rich". Heavy soot formation, higher fuel consumption and danger of serious damage to the catalytic converter are the result.
Thus, modern engine controls use an air mass sensor. It constantly determines the exact amount of oxygen atoms flowing in. This value is transmitted to the control unit. This then calculates the precise amount of fuel to be injected into the combustion chamber.
How does the air mass meter work?
Two different designs have established themselves among modern mass air flow sensors. Although they differ greatly from a technical point of view, both deliver equally reliable values. We distinguish between the thermal air mass meter and the Karman vortex air mass meter.
The thermal air mass meter has a platinum wire that is heated to a certain temperature. The passing air cools the wire down again. The temperature difference from a target / is comparison returns the value of the intake air mass. This is precisely calculated by the control unit.
A Karman vortex air mass meter determines the incoming airflow using a sound measurement rather than with the help of temperature. For this, air is initially calmed down by a honeycomb grille and then specifically swirled inside a vortex chamber. The resulting sound waves are detected using ultrasonic sensors. Based on this, the control unit calculates the air mass.
Japanese car manufacturers were the first to implement the Karman vortex air mass meter. Meanwhile, both construction principles have equally established themselves.
The mass air flow sensor is installed on the intake behind the air filter. As it is very sensitive to ingress of dirt particles, regular replacement of the air filter cannot be neglected.
Air flow meter defects
Air flow meters are purely sensory elements that have no moving parts. With proper maintenance, in particular of the air filter, they usually have a long life. Therefore, the most common type of damage to an air flow meter is pollution. This can usually be remedied with brake cleaner.
Another issue is damage to the air flow meter's housing. In technical language, the engine draws false air in this case. This leads to inaccurate measurements, which can manifest themselves in the form of a rough running engine or high fuel consumption. Sealing the leak with tape or epoxy is a temporary solution in such cases. Nonetheless, replacing the component guarantees a lasting solution against accidental intake of false air.
Contact damage on the electronics can lead to the same symptoms, but are reliably displayed when reading out the car's fault memory. If power cables are damaged, the rest of the engine space should also be checked. Most of the time such cable breaks are the result of racoon bites. Original parts ensure safety If cleaning the mass air flow sensor didn't yield success, replacement is usually the only option. Fortunately, such components can be obtained from brand-name manufacturers at low cost. Their replacement is very simple. Usually some needle-nose pliers and a Phillips screwdriver suffice for this task. The service life of air mass meter is rather long. Therefore, you should avoid cheap products and trust in brand quality instead. A replaced mass air flow sensor quickly pays for itself by saving fuel.