What are the Symptoms of a Bad Mass Airflow Sensor?

What are the Symptoms of a Bad Mass Airflow Sensor? Modern cars are designed with sensors that monitor other car components to ensure they are working well, and that the general performance of the car is not affected.

Some of these sensors are responsible for monitoring and regulating the flow of fuel and air into the engine to ensure combustion takes place properly. The mass airflow sensor falls into this category.

The mass airflow sensor shortened, MAF sensor is a vital part of the fuel injection system that is responsible for calculating the ratio of air that gets into the engine. This signal, when sent to the engine control unit (ECU), enables it to direct an adequate amount of fuel to the engine for combustion.

Like other car components, the MAF sensor can wear out over time. When this happens, it is important to replace it ASAP! As a vital component of a car, problems with the MAF sensor will cause so many inconveniences to the driver because of its sensitive function.

After a certain period of usage, the MAF sensor might develop faults and begin to show several symptoms of going bad. On this page, we discuss the symptoms of a bad mass airflow sensor.

What is the Mass Airflow Sensor?

The mass airflow sensor is a car component that calculates the quantity of air that gets to the engine.

It is a vital part of the fuel injection system that measures the air mass that gets into the engine and sends signals to the ECU to help calculate the quantity of fuel that will balance the quantity of air in the engine.

The MAF sensor sends this signal to the ECU. The control unit then uses the information to balance the ratio of air and fuel in the engine for combustion purposes.

The MAF sensor is found between the air filter and intake manifold and its working principle is quite simple.

The MAF sensor has two wires. However, only one is heated by an electrical current in the system and is usually described as a “hot wire” while the other operates at room temperature.

An electronic chip installed in the sensor calculates the air entering the engine by keeping the pressure of the hot wire at 200°F above that of the other wire.

When a driver presses the gas pedal, the throttle valve opens and allows air to flow over the MAF sensor’s hot wire. When the amount of air that goes over the hot wire is enough to cool it, more electrical current will be needed to keep it in its normal temperature.

The amount of electricity released is calculated by the electronic chip, it converts the electric current to the digital signals that are sent to the ECU. The ECU uses the signals to ascertain the amount of fuel that should be released by the fuel injectors to balance the air-fuel ratio and ensure the efficiency of the engine.

What are the Symptoms of a Bad Mass Airflow Sensor?

When the MAF sensor is bad, you will begin to experience some signs in your car.

The first sign of a bad mass airflow sensor would probably be the check engine light coming on due to sensitive nature of the component. Generally, a faulty MAF sensor will cause engine and driving issues.

Here, we discuss some specific symptoms of a bad mass airflow sensor.

Check engine light comes on

When the MAF sensor is faulty, the first symptom that might be noticed is the check engine light showing on the dashboard.

When the ECU receives wrong signals from the MAF sensor, it will trigger the check engine light as it will when other sensors are faulty. A faulty MAF sensor will throw codes like P0100, P0101, P0102, and P0103.

Rough or jerky acceleration

A faulty MAF sensor will cause an unbalanced air and fuel injection into the engine which will affect acceleration.

When the MAF sensor is faulty, it cannot detect the density of air and might send the wrong information to the ECU, causing the ECU to delay the release of air or release an inadequate amount, which will affect acceleration. Rough or jerky acceleration because of a MAF sensor can easily be noticed when you are driving on the highway.

A lean air-fuel mixture in the engine will make it difficult for your car to pick up speed.

Hard starting

If there is an inaccurate air-fuel mixture in the engine, you might find it difficult to start your engine. Engines are sensitive to the air and fuel mixture. So, if this mixture is wrong, it will become very difficult for the engine to start.

Reduced or increased fuel consumption

A faulty MAF sensor can affect the fuel consumption of your car.

The engine might begin to consume more or less fuel, and either case isn’t good for the car. An increase in fuel consumption will make  you to spend more on fueling the car. On the other hand, the engine can develop fault if it’s unable to take enough fuel needed for its optimal operation. Reduced fuel consumption can cause permanent damage to the engine.

Generally, abnormal fuel consumption will increase the rate of emissions from your car.

Black smoke from exhaust pipe

As stated earlier, too rich fuel in the engine will increase the engine’s emission.

A faulty MAF sensor will send wrong signals that will prompt the ECU to release too much fuel. When the fuel in the engine is more than the air, the excess fuel will burn out and release black smoke from the exhaust pipe.


Misfires occur when there is improper combustion.

For combustion to take place effectively, the engine must have the right ratio of air and fuel, compression, and ignition. Where the air-fuel ratio is inaccurate, some combustion cylinders will not ignite and will lead to engine misfire.

Rough idling

If a wrong amount of air and fuel is present in the engine, it will rough idle.

A rough idle means that you are getting more air and lean fuel. This is not good for the engine.

Testing and Diagnosing a Faulty Mass Airflow Sensor

Before replacing a MAF sensor, it’s important to conduct a test to ascertain if the sensor is faulty so that you don’t end up spending money on the wrong thing.

You should keep your service manual handy while doing this so you can always refer to it should the need arises.

Here are the basic steps to testing and diagnosing a faulty MAF.

  • Check for diagnostic trouble codes: If the faulty MAF sensor has caused the check engine light to illuminate, then you can pull out trouble codes from the ECU using a diagnostic scan tool. MAF sensor faulty codes confirms that the unit is bad.
  • Perform a visual inspection: This step will enable you to identify any problem with the wiring and connections, corrosion,  loose components, or a dirty sensor. Once you notice any of these, endeavor to fix them.
  • Use an OBD scan tool to check the airflow rate of the sensors. This is usually measured in grams per second.
  • Turn on your car and check for more data from the scan tool. The values should increase when you turn on the engine. However, if it is stable, then there is a problem with your MAF sensor or maybe the scan tool.
  • Check the voltage output of the sensor using a multimeter.
  • After inspecting and testing, and you notice faults, you should replace the sensor.

How to Clean a Dirty Mass Airflow Sensor

  • To clean a dirty MAF sensor, you will need clean towels, safety glasses, a screwdriver, and sensor cleaner.
  • Put on your sunglasses and locate the MAF sensor in between the air filter and intake manifold.
  • Loosen the clamps in the intake duct and the MAF sensor’s electrical connectors.
  • Pull out the MAF sensor from the intake manifold and place it on a clean towel.
  • Spray the MAF sensor cleaner on the sensor and clean it.
  • After cleaning, allow the sensor to dry then reinstall it.
  • Tighten the clamps on the intake and reconnect all electrical connectors.

How to replace a Faulty Mass Airflow Sensor

If the MAF sensor does not work after cleaning it, it needs a replacement.

Here are the procedures for replacing a faulty MAF sensor.

  • Put on your safety glasses and locate the MAF sensor.
  • Disconnect the electrical connectors and loosen the clamp from the intake duct.
  • Pull out the damaged MAF sensor from the intake duct and install the new MAF sensor of the same design.
  • Tighten the loosened clamp on the intake and reconnect the MAF electrical connector.

Cost of Replacing a Faulty Mass Airflow Sensor

The cost of replacing the MAF sensor depends on the model of your vehicle and where you get the labor done.

Usually, you should spend between $140 and $550. The sensor will cost between $100 and $400 while labor will cost between $40 to $150.

Frequently Asked Questions

Where is the Mass Airflow Sensor Located?

The MAF sensor is found on a large hose located between the throttle body and the air filter. If you are finding it difficult to locate the MAF sensor in your car, check the service manual for guidance.

Can I drive with a bad Mass Airflow Sensor?

No! It is not advisable to drive with a bad MAF sensor. This sensor will cause many problems to your engine as discussed earlier and can lead to hazardous situations.

How often should I replace the bad Mass Airflow Sensor?

The MAF sensor is designed to last the lifespan of your vehicle, as such, it does not have a particular service schedule. You should clean your MAF sensor at least after 100,000 miles and replace it when it is faulty.

What is the difference between Mass Airflow sensor and Air Volume sensor?

Sometimes, people get confused with these terms. The MAF airflow sensor and the air volume sensor are the same. When using any of the names, you are referring to the same thing. The MAF sensor is also referred to as a hot film meter or simply an airflow sensor.