What is a Mass Air Flow Sensor?
Yes, we’re talking about yet another three-letter acronym today.
Byline: Chris Teague
Your car has a variety of sensors that help control everything from how the air conditioner works to how much fuel enters the engine at any given point. When a problem arises with one of these sensors, it can be frustrating and concerning, but it’s not the end of the world. The mass air flow (MAF) sensor is one of the most important of the bunch, and even though it’s got a big job, it’s fairly easy to replace it yourself.
Because it plays such an important role in your vehicle’s fuel-delivery system, it’s vital to know the basics around the causes of MAF sensor problems, their symptoms, and how to fix them. Car Bibles’ editors are here to help, so stick around.
Let’s get rolling.
What Is a Mass Air Flow Sensor?
Mass air flow sensors, otherwise known as MAF sensors, are part of your car’s electronic fuel-injection system. As its name suggests, the MAF works to measure the quantity of air entering the engine. The MAF is typically mounted between the air filter and throttle body.
How Do MAF Sensors Work?
There are different kinds of MAF sensors, but in most cases today, the MAF is a hot wire-type sensor. This type of MAF uses a wire that is heated with electricity. A separate sensor nearby monitors the air temperature as different levels of throttle are used. As more air flows around the wire, it cools, and requires more electricity to maintain a constant temperature. The change in air temperature around the wire, combined with a separate reading of the level of electricity needed to heat it, are used to determine the amount of fuel that needs to be injected. This all functions within the parameters of the vehicle’s specified air-fuel mixture to keep the engine running properly and efficiently.
What Happens When a MAF Sensor Malfunctions?
Depending on the make and model of the vehicle, a MAF sensor problem could cause a variety of issues. The most common problems are:
- The engine cranks but won’t start
- The engine sputters or stalls
- There’s a lack of power or inconsistent power under acceleration
- There’s a sudden drop in fuel economy
What Causes MAF Sensor Failure or Problems?
This will again depend on the type of car you have. In all vehicles, however, a contaminated sensor is one of the most common causes of failure. Dirt and road debris can get into the sensor, and sometimes moisture can cause degradation or corrosion. Other causes include excess vibration causing damage, a short or fault in the connections, or disconnected wiring.
How Much Do MAF Sensors Cost To Fix?
You may find a repair price tag of anywhere between $100 and $400, depending on the type of vehicle you own and where you take it to be fixed. The good news is that replacing a MAF is not the most difficult home repair project you could undertake, so you’ll likely be able to do it yourself. The part is generally easily accessible and can be swapped out by an amateur mechanic. Keep in mind that the cost of the part makes up the vast majority of the professional repair costs, so doing it at home will only save you labor cost. Expect a savings of somewhere between $50 and $100 if you DIY the replacement.
Can I Drive With a Bad MAF Sensor?
Even if you can start and move your car with a bad sensor, we strongly advise you not to ignore the warning signs. Being able to start and drive your car is not a sign that it will continue running or that it’s safe to drive. Stalling at highway speeds or having issues with acceleration not only puts you at risk, it also puts everyone else around you at risk.
Beyond safety, it’s just not smart to drive around with a vital part of your car’s fuel-injection system malfunctioning. Bad gas mileage and potential damage to other parts of your engine should be enough motivation to get the problem fixed.
Car Bibles’ Glossary of MAF Sensor Terms
Welcome to Bibles school!
The air-fuel mixture, or air-fuel ratio, is the ideal combination of both air and fuel to achieve a complete burn during combustion. Different engines rely on different air-fuel mixtures to operate properly. If the mixture has too much fuel, it’s said to be rich. If there is too little fuel in the mixture, it’s known to be lean. Sensors throughout the vehicle keep the car operating with the optimal air-fuel mixture.
Fuel injection refers to the system that delivers fuel from a car’s tank to its engine. In general, pumps move fuel to the engine, where it is then sprayed into the manifold by an injector. Fuel injection took over for the carburetor and allows for more precise control over fuel delivery, better fuel efficiency, and lower emissions.
When your engine stalls, it means that it suddenly stops working. If you drive a car equipped with a manual transmission, it might stall because you didn’t properly use the clutch. If that isn’t the case, a stall could be related to air flow or fuel-flow issues. A car should never unexpectedly stall while driving.
Fuel economy refers to the number of miles that can be traveled on a gallon of fuel. This number ranges wildly from vehicle to vehicle and can be quite high or low, such as in the case of small hybrid cars or large SUVs, respectively.
OBD2, or onboard diagnostics, is a system of vehicle sensors and computers that monitor and control various systems. This can include emissions and engine metrics, such as the air-fuel mixture. The system generates error codes that correspond to various vehicle problems, which can be read using an OBD scanner tool.
The Car Bibles Questionnaire
Q. Will I see a check-engine light (CEL) if my MAF sensor is malfunctioning?
A. In most cases, yes, but it’s not guaranteed. The car’s computers are constantly monitoring the air-fuel mixture and even the sensors themselves, so you’re likely to see a CEL if you have MAF problems. Like the alphabet soup?
Q. Can I disconnect the MAF?
A. If the MAF sensor has a problem and is directing the wrong mixture of air and fuel into your engine, unplugging or disconnecting it might temporarily solve the problem, but it’s not a solution. Some people report that unplugging the MAF sensor puts their cars into limp mode, which is a severely reduced power setting, but this is far from a guaranteed outcome. You may end up with a car that won’t start. Never drive with a disconnected MAF sensor.
Q. Can I adjust the air-fuel mixture?
A. You can, and there are several guides for doing so online, but be aware that fiddling around with your engine’s operations requires know-how. If you are unfamiliar with how your engine works or if you’re unsure of the mixture you should be targeting, it’s best to consult a mechanic or to research solutions for your specific vehicle.
Video on MAF sensors
Car Bibles’ Favorite MAF Sensor-Related Products
Fixing a MAF sensor can seem like a daunting task, especially if you don’t have the right tools on hand. That’s why Car Bibles’ editors have gathered a few of their favorite products to help you get started. They include Mechanix Gloves, the Innova CarScan Advisor 5210 OBD2 Code Reader, and Haynes Repair Manuals (model-specific).
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