An engine requires the mass air flow (MAF) sensor to work efficiently. The MAF sensor analyses the amount of air that enters the engine and transfers retrieved data to the powertrain control module (PCM), which uses this data to regulate the fuel injection rate. This article describes the bad MAF sensor symptoms, causes, and how to reset the mass air flow sensor.
What is MAF Sensor?
The MAF sensor, or Mass Air Flow sensor, is used to measure the mass flow rate of air entering a fuel-injected IC engine.
The density of the air varies with the pressure and temperature. The air mass data is very important for the powertrain control module (PCM) to balance the air-fuel ratio and transfer the precise fuel mass to the combustion chamber.
In various vehicles, the density of the air changes with the forced induction, altitude, and ambient temperature. That’s why efficient MAF sensors are important to determine the amount of intake air in every cylinder.
Bad MAF sensors can initiate different problems within the engine and result in poor engine performance and poor fuel economy.
The air-fuel ratio of the engine can be controlled precisely with the associated functioning of the MAF sensor and O2 sensor. The mass flow sensor delivers the exact air flow information to the PCM, and the O2 sensor makes the changes in this information to make it even more precise. Your PCM utilizes the data of the MAF sensor to regulate the air-fuel ratio, fuel injection rate, and engine performance.
How does a MAF Sensor work?
The MAF sensor is located between the throttle body and the air filter of your car. It measures the air that enters the engine of your car. The hot wire theory serves as the foundation for the MAF sensor’s operation.
The majority of automobiles contain hot-wire MAF sensors. This sensor has two basic wires: an ambient temperature wire and one heated wire. The electric current is used to heat one of its wires while the other remains unheated. The heated wire cools when the air travels over it.
With the change in temperature between these two wires, the mass air flow sensor automatically adjusts the current to the heated wire to maintain the temperature. This adjusted current is then converted into voltage and forwarded to the PCM of your car. These voltages depict the readings of the airflow. The PCM uses these readings to adjust the amount of air entering the engine.
The PCM then directs the injector to supply the precise amount of fuel that is proportionate to the airflow, resulting in an air/fuel combination that is appropriate for your engine.
Symptoms of a Bad MAF Sensor
The bad mass air flow generates multiple symptoms, like a low vacuum and low compression. A bad MAF will also exhibit symptoms comparable to those caused by a low fuel pressure caused by a damaged fuel pump.
As the MAF sensor goes bad, it produces one of the below-given symptoms:
- Check Engine Light illumination
- Bumpy or Jerky Acceleration
- Acceleration Problems
- Hard Starting
- Rough Idle
- Poor Fuel Economy
- Black Smoke from Exhaust Pipe
- Failed Emission Test
1) Check Engine Light illumination
The illumination of the check engine light is one of the first symptoms of a bad MAF sensor.
The Powertrain Control Module (PCM) of the car manages the readings of all the sensors present in the car to ensure the efficient working of your engine. If any of the sensors send incorrect data to the PCM, the check engine Light illuminates.
As the MAF sensor goes bad, it sends wrong information to the PCM, and your PCM will instantly illuminate the check engine light on your dashboard.
There is also a chance that the PCM may not detect the bad MAF sensor for some reason, and the check engine may not illuminate.
Read More: Car Dashboard Warning Lights and Symbols
2) Bumpy or Jerky Acceleration
A faulty mass air flow sensor may cause an incorrect air flow and may produce bumpy or jerky acceleration.
This is mainly because the air-fuel combination gets too lean, causing the automobile engine to starve and trigger jerks.
If the air-fuel combination is excessively rich, it will quench the spark plug’s ignition, resulting in rough or harsh acceleration.
3) Hard Starting
Difficulty starting your car is also a sign of a bad MAF sensor. There should be the perfect airflow mixture provided to the car at the perfect moment to start a car smoothly. So, if the car fails to get that perfect airflow, it will not be able to start, and you will face hard starting conditions.
4) Acceleration Problems
Sometimes you may find it difficult to accelerate your car. Trouble in acceleration is one of the major symptoms of a bad mass air flow sensor.
A precise air-to-fuel mixture in the combustion chamber is needed for the best engine performance. A bad air-fuel mixture can result in a bad sensor and affect the performance of the car.
5) Rough Idle
A smooth idle can only be achieved with the proper amount of fuel in your car. With the bad MAF sensor, the system will be unable to run smoothly during the idle state.
6) Poor Fuel Economy
When the MAF sensor fails, it does not deliver the correct signal to the PCM. As a result, sometimes the engine runs rich and consumes more fuel than usual, causing poor fuel economy.
7) Black Smoke from Exhaust Pipe
If you ever experience black smoke from the tailpipe or exhaust pipe, it may be due to the higher fuel consumption of the engine than usual. So, the excessive black smoke is a sign that the engine is running extremely rich. This can be caused by a bad MAF sensor.
Not only black, but the grey smoke can also cause the engine to run rich. It can also damage the catalytic converter of your car. The catalytic converter is an expensive component, so it is recommended to carefully resolve this issue before it’s too late.
The main reason for the misfire is the failure of the cylinders to burn the fuel properly. Perfect air-to-fuel ratio, compression, and ignition are required for proper fuel combustion.
Hence, if the air-fuel ratio mixture highly deviates from its actual value, it will result in the cylinder failing to ignite. This failure will eventually result in misfires. If you discover any issue codes connected to misfires, it might be an indication of a faulty mass air flow sensor.
9) Failed Emission Test
When the MAF sensor of your car goes bad, it may send the wrong data to the PCM, indicating a low or high engine load. The vehicle engine requires a specified amount of air-fuel mixture to control the exhaust emissions. A faulty MAF sensor leads to a poor air-fuel ratio and increases the level of exhaust emissions.
Read More: Bad MAP Sensor Symptoms and Causes
Where is MAF Sensor Located?
The mass air flow sensor is located between the engine’s intake manifold and the air filter.
The location of the MAF sensor varies depending on the model or the manufacturer of the vehicle. Basically, the MAF is fitted as per the engine design. You can go through the repair manual and the internet for an exact and fast search.
How to Test a Faulty MAF Sensor?
MAF sensors are expensive, and it is recommended to carefully diagnose or test a bad MAF sensor before replacing it.
Follow the below-given steps in order to diagnose the MAF sensor:
- Use the OBD2 scanner to check the live data from the MAF sensor in the idle state. Its value must be 0 mg.
- Now, start your car and check these values again. The values should increase while reversing the engine and decrease with the decrease in RPM. But if the values are steady, it shows a problem with the MAF sensor or its wiring.
- Check for rust by removing the sensor plug.
- Measure the wirings and the sensor using the repair manual.
- Inspect and replace the corroded or damaged wirings.
- In case of a faulty MAF sensor, replace or clean it accordingly.
- Now clean the mass flow sensor with the help of the cleaner or alcohol and rest it for about 18 minutes. Make sure to perfectly dry the sensor before reinstalling it in your car.
MAF Sensor Replacement Cost
The replacement cost of the MAF sensor varies according to the vehicle model, labor cost, and type of brand.
The average replacement cost of a mass air flow sensor is between $90 and $400. The cost of the part is about $50 to $320, while the labor costs are from $40 to $80.
|$40 to $80
|Cost of Part
|$50 to $320
|MAF Sensor Replacement Cost
|$90 to $400
How to clean a MAF Sensor?
Follow the below-given steps to clean your MAF sensor:
- Disconnect the sensor: let the engine cool after turning off your engine and removing the key from the ignition slot. Look for the MAF sensor. Disconnect the sensor from the car’s system.
- Remove the Sensor: Once the sensor is disconnected, loosen the clamps and drag the sensor assembly far from the tubing. Now remove the sensor from the air intake boots.
- Clean the Sensor: Take a towel and place the sensor on it. Now use the cleaner to clean it properly from the inside.
- Reinstall the Sensor: Let your sensor dry completely. Now, reinstall the dried sensor in its place. After placing it, tighten the clamps and the brackets.
- Test Drive: Perform a test drive to check the performance of your MAF sensor.
Frequently Asked Questions
What is the function of the MAF Sensor?
The Mass Air Flow sensor, often known as the MAF sensor, is used to calculate the right air-fuel mixture by determining the mass flow rate of air going into the internal combustion engine. The MAF sensor helps in increasing the engine’s efficiency.
How often do MAF sensors go bad?
The MAF sensor in your car should be replaced after driving from 10,000 to 12,000 miles. The life of your MAF sensor can be prolonged with regular air filter replacement and proper maintenance. Although the expiry date of the MAF sensor is not mentioned anywhere.
What happens if the Mass Air Flow sensor fails?
The MAF sensor is an important part of the engine of your car, and if it fails, it may lead to many problems. Poor engine performance, uneven idling, control lamp failure, and poor fuel economy are some of the major issues that originate with the bad MAF sensor.
What are the Causes of a bad MAF Sensor?
Vacuum leaks and contamination are the major cause of the bad MAF sensors and require replacement. As contaminated air, dirt, and other debris get into the sensor, the parts become contaminated and fail.
How to reset Mass Air Flow Sensor?
- Park your vehicle in a safe place.
- Locate your vehicle’s mass air flow sensor. Look at your manufacturer’s manual to find the exact location of the MAF sensor.
- To prevent short circuits or damage, disconnect the negative battery terminal before working on electrical parts.
- Remove all the clamps or screws that hold the sensor in its place.
- After removing the screws, carefully remove the sensor.
- If your MAF sensor is dirty, clean it properly.
- If your sensor is badly damaged, you should replace it.
- Reinstall the new sensor in its original place and secure it with clamps or screws as necessary.
- Now, reconnect the negative battery terminal and perform a test drive to check the performance of your MAF sensor.
Can I drive with a bad MAF sensor?
Yes, you can drive with a bad MAF sensor for a limited time. It is always recommended to fix the bad sensor to prevent long-term engine problems.
Can a mass air flow sensor cause transmission problem?
Yes. Stalling, no start condition, low power, and reduced acceleration are some of the transmission problems that your car may face with a bad mass flow sensor. Similarly, the bad mass air flow sensor can affect the automatic gear shifting patterns.
How long does a mass air flow sensor last?
Mass airflow sensors are built to last throughout the life of your vehicle. In truth, there is no fixed replacement interval for the MAF sensor. As a result, the sensor is typically not changed until it fails. But it is always recommended to replace the MAF sensor after 10,000 to 12,000 miles.
What are the signs of a bad Mass Airflow Sensor?
- Check Engine Light illumination
- Engine misfiring
- Black Smoke from the exhaust pipe
- Jerky acceleration
- Acceleration issues
- Poor fuel economy
- Vehicle starting issues
- Rough Idle