The mass air flow sensor is prone to failure due to age or other factors affecting its performance. Common pollutants like dirt and dust are the major reason behind a failing air flow sensor.
However, seeing as it functions all the time when you run your car, it is understandable that the sensor often fails sooner rather than later.
It is also possible that a voltage surge from the car battery fries the circuit inside the sensor and it is unable to transmit any information to the car’s onboard computer.
At the end of the day, it is the ECU which decides what action to take and whether the mass air flow sensor has lost its efficiency. If the ECU suspects any fault, you are notified via a warning light (also called the check engine light), that is illuminated in the car’s dash.
What is a Mass Air Flow Sensor?
Engines use a mixture of air and fuel to operate. Without either one of them, the engine’s performance will be affected. To measure the amount of air that flows into the engine, automotive engineers have installed mass air flow sensors. These sensors calculate the air coming in and send the information to the car’s onboard computer, called the ECU, to analyze.
Based on the valuable information received from the air flow sensor, the ECU makes the appropriate adjustments to the fuel and air ratio.
Common mass air flow sensors have a very simple design. The sensor has two wires inside, of which one is heated and the other left cold. The MAF system measures air through a unique method. It does that by determining the amount of current needed to keep the heated wire at a temperature of 200F from the cold wire.
The MAF will change the amount of current that enters the wire and using this method, the amount of air will be either be increased or decrease.
Signs of a Bad Mass Air Flow (MAF Sensor)
As the mass air flow sensor is directly linked with the engine, any issue with it can result in disruptive performance. There are some common symptoms which occur when the MAF sensor gets damaged and we will discuss them here.
The most common symptoms from a bad mass air flow sensor are slow acceleration and reduced engine power. You can also notice a difference in the fuel economy as the main function of the mass air flow sensor is to let the engine know how much fuel it should inject.
1. Check Engine Light Illuminates
The most common sign is that the check engine light illuminates signalling something wrong with the sensor and the engine. The check engine light also blinks due to many other reasons, so it is best to have your car scanned for a trouble code.
2. Lean Idling
Lean idling occurs when too much air is sourced by the engine while the amount of gasoline is less in comparison. Due to the abundance of air, the combustion process does not take place properly, causing a problem with the engine. This problem occurs mainly when the MAF sensor gets dirty and has a contaminated wire. The easy fix is to have the sensor cleaned by a technician.
3. Engine Does Not Start Properly
When turning on the ignition, if your car does not start immediately, it may be due to a bad mixture of air and fuel. It is also recommended to have your spark plugs inspected to identify the exact reason for the poor starting.
4. Engine Drags
If you notice that your car’s engine drags when an extra load is added, it may be due to a faulty MAF sensor. If more than the usual weight is added on the car, the engine uses more gasoline in order to run effectively and with a faulty MAF sensor, the PCM will not determine the right amount of fuel/air mixture causing the engine to drag.
5. Delay in Acceleration
A damaged MAF sensor causes a problem with the acceleration at higher speed. If you notice some delay when you step on the gas pedal and the car’s acceleration, it is because of the lack of gasoline reaching the engine. A faulty MAF sensor disrupts the air/fuel mixture, decreasing the engine’s performance.
6. Excessive Fuel Consumption
The MAF sensor constantly checks the amount of air flowing into the engine and this helps the engine decide on the right amount of gasoline needed for combustion. A faulty MAF sensor can give an incorrect reading to the PCM, causing the engine to consume too much gasoline.
|Bad mass air flow sensor||Rough Idle|
Low engine performance
Check Engine Light
Hard starting condition
Excessive Fuel Consumption
|Faulty mass air flow sensor wirings |
Corrosion in the connector to the sensor
Faulty Mass Air flow sensor
|Repair faulty wirings to mass air flow sensor |
Clean the connector to the sensor
Replace Mass air flow sensor(MAF)
Where is the MAF Sensor Located?
The MAF sensor can either be found in the intake or just before the throttle body. Its location varies from manufacturer to manufacturer, as they fit the sensor based on the engine’s design.
You can use the service manual to be sure of the location, or use the internet for a quick search. Check the picture for a clue as to where it can be located.
Repairing/Replacing a Mass Air Flow Sensor
To replace a MAF sensor, you need a bit of professional insight. It is not easily found nor easily replaced. However, with the proper tools and the right mindset, you can achieve anything. Here I what you need to do:
- Locate the mass air flow sensor. Use the service manual if needed
- Remove the electrical connectors from the sensor before you attempt to replace it.
- Use a screwdriver to unscrew the screws on the sensor and remove the clamp that holds it in place
- A clamp can also be removed using a wrench
- Clean the area with a cloth or use a blower to clear off the dust from the surroundings
- Match the old sensor with the new one
- Install the new sensor and tighten the screws back
- Make sure not to make it too tight
- Attach the connector back to the sensor
- Use an error code scanner to clear the error code that comes from a failing MAF sensor
- Start your car and see if the check engine light illuminates
- If it still does, you weren’t able to install the sensor correctly in which case you need to repeat the process
Diagnosing a Failing Mass Air Flow Sensor
Fortunately, sensors show signs of failure. If you know what to look at, you can easily identify the issue and make the replacement. Your car will burn more fuel than usual when it’s idling. If you are filling up the tank more frequently than you used to, it is time to get the mass air flow sensor checked.
A failing MAF sensor will also affect your car’s performance. You won’t be able to accelerate quickly or start your car in the first place. A lot of misfiring will also be witnessed.
The check engine light usually illuminates when the MAF sensor goes bad.
Another way to diagnose the failing mass air flow sensor is to try to clean it; check the section down below.
Cleaning a Dirty Mass Air Flow Sensor
Often, the problems associated with the mass air flow sensor occur due to dirt and debris buildup. This particle accumulation over time results in poor performance of the sensor. The MAF sensor should be cleaned and serviced every six months or whenever you change the engine oil. Moreover, it is a good practice to clean or change the air filter along with the MAF sensor as well. Here, we will highlight 3 simple steps required to clean the mass air flow sensor.
• Flathead screwdriver
• Plastic bag
• Alcohol (for cleaning)
• MAF sensor cleaner (optional)
Removal of the Sensor
The MAF sensor is often located inside or after the car’s airbox and it can be easily removed using a flathead screwdriver. Always remember not to touch the connecting wires as they are delicate and if broken, you’ll need to buy a new sensor.
Cleaning the Sensor using alcohol or cleaner
To clean the MAF sensor, there are two methods; the first technique is simple and requires a plastic bag and alcohol. Place the sensor in a plastic bag and rub it with alcohol to clean any dirt on it. The second technique is to buy a mass air flow sensor cleaner spray from a nearby auto store and use it to clean the sensor. One recommended cleaner is the CRC 05110 Mass Air Flow Sensor Cleaner – 11 Wt Oz. which can be found on the link on Amazon. It is specially designed to clean MAF sensor wires.
Reinstall the MAF Sensor
Once the MAF sensor is cleaned, let it dry for a couple of minutes. After about half an hour, install the MAF sensor again and start the engine.
Video of MAF sensor cleaning:
Testing a Bad MAF Sensor
If the check engine light illuminates on your dashboard, it is time to visit the nearest auto-shop and have your car scanned for trouble codes. The mechanic will use a scan tool to check what trouble code is retrieved. The trouble codes from P0100 to P0104 all indicate that something is wrong with the mass air flow sensor. The trouble codes P0171 and P0174 are also caused due to a damaged or faulty mass air flow sensor.
Another procedure to check the mass air flow sensor is using a voltmeter. To test the sensor, connect it to the voltmeter and measure the signal at different engine speed and compare it with the specific range. If your car produces a digital signal, use a scan tool to read the data. Once you have taken the reading of your sensor, replace it with a new sensor and check again to notice the difference. If there is a significant difference, it means the sensor is faulty and should be changed.
MAF Sensor Replacement Cost
A Mass Air Flow Sensor is not so cheap but it is not very expensive either. You could get one for $120 – $300 to which you should add labor costs of $80 – $100. Therefore, on average you are expected to pay $200 to $400 in total for a mass air flow sensor replacement.
The price you get for the replacement can vary due to a variety of factors.
Firstly, the part itself can come in a variety of qualities. You can get a genuine air flow sensor or you could get off-market sensors. Both would work well but it is possible the cheaper one will go bad sooner than the more expensive option. Moreover, the cheaper quality may not match with your car and your ECU might reject it. Therefore, it is best to go for genuine parts rather than going for cheap aftermarket ones.
The second factor is the make and model of your car. Imported cars usually have very expensive parts; because, as you would expect, their parts are also imported. You get the car part after a number of taxes are levied on it. So, it is natural for you to pay more for such a car. However, if your car is locally assembled, the chances are that you will be let off pretty cheaply. That is why we have listed the price as a range and not as one single figure.
The third factor is the labor cost your mechanic charges you. Mechanics are either certified or they are self-taught. It is obvious that the certified mechanic has more credibility since he has a certificate to prove his worth. A self- taught mechanic will have nothing to his name, which means you would be gambling on your chances. The certified mechanic will also charge you a high price, but once you give them your car, you can rest assured that whatever the problem is your car will be gone.