What is the Mass Air Flow (MAF) Sensor?

A vehicle’s engine works on the basic principle that requires both air and fuel to work in tandem with each other. The air and fuel mixture must be in the right proportion to achieve optimal combustion and allow the engine to perform as needed.

Carburetors were once the device that controlled the air flow and fuel mixture ratio.  The days of that being the device are a thing of the past. Since the mid-1990’s, cars manufactured with an engine control unit, or ECU, (sometimes referred to as the engine control module, or ECM) use sensors to measure the air flow.

The engine control unit collects data from various sensors. One of those sensors measures the amount of air entering the throttle.  The location of the sensor is after the air filter and before the throttle body. The mass air flow sensor measures the amount of air entering the engine. The ECU utilizes this information to calculate and deliver the proper amount of fuel to the cylinders under the various operating conditions.

Needless to say, the mass airflow sensor is critical to the engine’s performance.

Four Types of Mass Air Flow Sensors

There are four main types of air flow sensors:

  • Vane Air Flow Meter
  • Hot Wire Sensor
  • Cold Wire Sensor
  • Kármán Vortex Sensor

The vane air flow meter and hot wire sensor are the most common in cars and we will focus on those.  Read on to see how they work.

Hot Wire Air Flow Sensors

The hot wire air flow sensor consists of a small, electrically heated platinum wire. The platinum sensing wire is hundreds of degrees hotter than the ambient air intake temperature as measured by the intake air temperature (IAT) sensor. The intake air flowing cools the sensing wire. In return, the MAF signals to the ECU the amount of air flow coming in the engine.

An idling engine has a minimal amount of air flowing around the sensing wire in the hot air flow sensor. Therefore, it requires a minimal amount of electric current to keep the platinum wire hot.

In contrast, a pressed gas pedal opens the throttle and more air enters the air intake. The additional air flowing around the sensing wire cools it down. As a result, the platinum wire requires a higher electrical current to maintain the set temperature.

The electrical current needed to keep the air flow sensor wire hot is proportional to the amount of air flowing through the air intake. The mass air flow sensor translates the electrical current needed to keep the wire a certain temperature into a digital signal and sends the data to the engine control unit. The ECU then determines the amount of fuel to inject into each cylinder based on the optimal air to fuel ratio.

These types of sensors are popular among major vehicle manufacturers like Chrysler, Toyota, Honda, and Ford in their cars.

Vane Air Flow Meter

The vane air flow meter utilizes a vane (sometimes referred to as a flap or door) placed in the air stream of the engine air intake opening. In the resting position, a spring holds the vane closed. With a pressed throttle (gas pedal), the vane opens and air enters the engine.  As the volume of air entering the engine increases, the vane proportionally pushes open.

The vane is also connected to the slider of a potentiometer.  As air enters the engine displacing the vane, the slider moves between a power supply and a ground. A voltage signal sent to the engine control unit corresponds to the position of the slider. Thus, the ECU measures the air flow as it enters the combustion chambers.

Many vane air flow meters have an idle mixture screw.  This screw controls the quantity of air that bypasses the vane.  Consequently, the fuel mixture richness or leanness can be adjusted.

Vane airflow sensors are found mostly on German import vehicles, Japanese import vehicles, and certain Ford vehicles.

Symptoms of a Faulty Mass Air Flow Sensor

The mass air flow sensor plays a vital role in the engine’s proper function. The data from the MAF determines the ratio of the air-fuel mixture. Hence, it directly affects the fuel economy of your car. A slight miscalculation by the MAF can offset the engine’s efficiency allowing it to burn more fuel or less fuel than optimal.

Mass air flow sensor problems can be troubling for your car, which is why you should be aware of the symptoms. Other parts of the vehicle, such as the catalytic converter, could be damaged.  As soon as you start noticing signs, a professional mechanic at Autopractor, the top rated auto repair shop in St. Charles, IL, will check the airflow sensor and get your vehicle back optimal performance.

An Illuminated Check Engine Light

The check engine light (CEL) is one the most common indicators of a problem in your car. The yellow check engine light illuminated on your dashboard indicates the on-board computer diagnostic (OBD) system has diagnostic trouble codes (DTC) stored. A scan tool is needed to view the trouble code(s).

While more than a malfunctioning MAF sensor will illuminate the CEL, you should schedule an appointment at Autopractor for a check engine light diagnosis.

Common trouble codes that indicate a faulty mass air flow sensor include:

Common MAF Trouble Codes

  • P0100: MAF circuit malfunction
  • P0101: MAF circuit range or performance problem
  • P0102: MAF circuit low input
  • P0103: MAF circuit high input
  • P0104: MAF circuit intermittent
  • P0171 system too lean (bank 1) and P0174 system too lean (bank 2) are also often caused by a faulty or contaminated MAF sensor.

As previously mentioned, a faulty mass air flow sensor can cause the CEL light to come on. In this scenario, the MAF sensor is sending incorrect readings to the engine control unit (ECU). Obviously, a damaged sensor should be replaced.  At times, it is not damaged and a thorough cleansing of the sensor with products such as CRC Mass Air Flow Sensor Cleaner will resolve the issue.

Unusual Idle

Unusual, or rough idling usually arises when the mass air flow sensor is allowing too much air into the engine resulting in the engine to run lean. Too much air into the engine means there is not enough fuel to maintain proper, ongoing combustion.

A dirty sensor will also cause a rough idling engine. Clean a dirty sensor using a hexane-based solution. CRC Mass Air Flow Sensor Cleaner is one such cleaning solution. However, consult with an ASE certified technician at Autopractor in St. Charles for a professional diagnosis.

Problems with Ignition

If the MAF sensor malfunctions, you might experience problems with starting your car. The engine might not be getting the exact amount of air to complete the air-fuel mixture. It may take you several tries before you can ignite the engine.

Such a problem can be an early symptom of a malfunctioning MAF sensor. If you want to save yourself from wasting time stranded in the middle of nowhere, you should get your car checked by an ASE certified mechanic at Autopractor in St. Charles, Illinois.

Loss in Power

The biggest indicator of a bad MAF sensor is a loss in power or acceleration. You might feel this when you press the accelerator pedal and your car barely moves. The same issue can arise if the engine is not getting sufficient fuel. Instead of speculating and wasting time, call Autopractor to book an appointment and get a proper diagnosis.

Superfluous Fuel Consumption

If everything in your car feels fine, the acceleration is good, there are no problems with ignition or idling, but you are visiting the gas station more often, there is a high probability your MAF sensor is not functioning properly.

The airflow sensor can sometimes send incorrect readings to the ECU resulting in your car running a rich air/fuel mixture. When this happens, you do not feel a loss in acceleration or a drop in performance. In fact, you may feel your car is running better than before. However, there is an underlying problem that you are unaware of, and that is causing fuel to be wasted.

When you feel your gas station visits are frequent and you are achieving mileage below the average from your car, then you should get your MAF checked by an ASE certified automotive technician at Autopractor in St. Charles, Illinois.

Mass Air Flow Summary

The mass air flow sensor has a crucial job in the big scheme of things. In reality, the sensor plays such a significant role that without it, your car is worthless. This small piece of technology keeps your engine healthy and the environment clean. However, if it malfunctions, you risk a lot. 

Fortunately, sensors are easy to clean and are relatively inexpensive to replace. You can clean a sensor yourself if you wish to embark on the endeavor. Alternatively, your ASE certified auto technician is always available at Autopractor.

Is My Mass Air Flow Sensor Functioning Properly?

Do you suspect issues with your mass air flow sensor?  Autopractor is the expert in St. Charles for diagnosing, cleaning, and replacing your mass air flow sensor. Call Autopractor today at 630-444-1414.

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