Bad MAF Sensor (Signs, Causes, Fixes)


The mass airflow (MAF) sensor regulates the amount of air flowing into your vehicle’s engine which, in turn, regulates the amount of fuel being injected. If the MAF sensor fails, it can lead to either an overflow or a restricted flow of air, causing the engine to run lean and hot or rich and cold. In either case, this can lead to engine damage and reduced fuel efficiency.

Although it’s possible to drive with a bad mass air flow sensor, it’s inadvisable to do so, as it can cause widespread engine damage. Over time, an engine that runs rich or lean will lose power, stall, rough idle, and generally perform poorly. If left for too long, dangerous hiccups can lead to long-term and serious damage that become costly to repair.

If you suspect that your vehicle’s MAF sensor has stopped working, continue reading to learn more about the problem. In this guide, we’ll explain what the mass air flow sensor does, why it sometimes goes bad, how to tell if it’s malfunctioning, and what to do to fix the issue. Until you are certain that the sensor is working properly, we don’t recommend driving.

MAF Sensor Related: Understanding & Dealing With Limp Mode

What is the MAF Sensor and How Does It Work?

The MAF sensor is located in the engine’s air intake system and measures the amount of air entering the engine. It then sends this information to the ECU, which uses it to calculate the amount of fuel to inject. This data helps to determine how much power the engine will produce. More air means more oxygen, and more oxygen means that the engine can burn more fuel.

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The MAF sensor is usually a hot-wire type sensor, which means that it uses a heated wire to measure the airflow. As air passes through the sensor, the wire is cooled by the air, and this change in temperature is used to calculate the amount of air entering the engine.

If too much air is allowed to flow into the system, it can lead to a loss of power and performance, potentially damaging the engine if left uncorrected. Likewise, if the engine receives too little air, it will struggle to efficiently combust fuel, leading to poor fuel economy and sudden stalling. For these reasons, the MAF sensor plays a vital role in regulating engine performance.

Related: Bad MAP Sensor Symptoms

What Causes the MAF Sensor to Go Bad?

There are several reasons why a MAF sensor can fail, but the most common is simply due to age and mileage. Over time, the hot wire can become coated with dirt and grime, insulating it and preventing it from cooling quickly. This will cause the sensor to report a weaker airflow than is actually the case, and the engine will run lean as a result.

Another common cause of MAF sensor failure is an electrical problem. If the wires or connectors become corroded or damaged, it can cause the sensor to malfunction. This is often the case in older vehicles where the wiring harness has not been well-maintained.

In some cases, the MAF sensor itself may simply go bad and need to be replaced. This is usually not the case with newer vehicles, but it is something to keep in mind if you have an older car that’s not been well maintained over the years.

Signs of a Bad MAF Sensor

A failing MAF sensor can cause a host of problems that progressively become worse the longer you leave the bad sensor in place. To avoid long-term damage, keep an eye out for the following signs and consult with a mechanic if you’re concerned that your vehicle’s mass air flow sensor has gone bad:

  1. Check Engine Lights: If your vehicle has issued a check engine light, take it to the nearest auto parts store or mechanic and have them check the diagnostic codes. A bad MAF sensor will throw one or more codes between P0100 and P0103.
  2. Reduced Fuel Efficiency: A failing MAF sensor can cause the engine to run lean, which means that it will require more fuel to run correctly. This will result in reduced fuel economy and you’ll notice that you’re filling up the tank more often than usual.
  3. Rough Idling: If the MAF sensor is not sending the correct information to the ECU, it can cause the engine to run lean or rich, leading to a rough idle. You may also notice that the engine suddenly surges while you’re driving.
  4. Sudden Stalling on Acceleration: If the engine is not receiving the correct amount of air, it can cause the engine to stall without warning. This can be dangerous if it happens while you’re driving and can lead to accidents.
  5. Black Exhaust: If the engine is running too rich, it will cause the fuel to burn inefficiently, leading to black exhaust smoke. This is a sure sign that something is wrong with the engine and should be checked out as soon as possible.

If you experience any of these issues while driving, have your vehicle checked as soon as possible. The sooner you fix the underlying problem, the better off your engine will be.

What Happens If You Ignore a Bad MAF Sensor?

If you continue to drive your vehicle with a bad MAF sensor, it can lead to long-term damage to your engine. If the sensor is not sending the correct information to the ECU, it can cause the engine to run too lean or too rich, leading to engine knock, pre-ignition, and pinging. It can even cause your car to turn off while driving, which is really dangerous in itself.

If left unchecked, these problems can cause serious damage to the engine, potentially leading to engine failure. In some cases, the damage may be severe enough that the engine will need to be replaced, which can be very costly.

How to Fix a Bad MAF Sensor

Although it’s possible to clean a dirty MAF sensor, in most cases, the only way to fully fix the problem is to replace the part entirely. This is a relatively simple and inexpensive repair that can be done at home with a few tools, or you can take it to a mechanic and have them do it for you.

To replace the MAF sensor, you’ll first need to locate it in the engine bay. It’s usually located near the air filter box or close to the throttle body.

  1. Once you’ve found it, disconnect the electrical connector, and unscrew the sensor from its mount.
  2. Next, take the old sensor to an auto parts store and purchase an exact match.
  3. Once you have the new sensor, install it in the same location as the old one and reconnect the electrical connector.
  4. Start the engine and see if the check engine light is still on.
  5. If it is, take the vehicle to a mechanic and have them check the codes to see if there are any other issues that need to be addressed.


If you do decide to clean the sensor, proceed with caution and research. The MAF sensor is not something you want to mess with. They are really fragile, and some cleaners can leave a residue on the wire in the sensor, resulting in incorrect readings.

The Bottom Line

A bad MAF sensor can cause all sorts of problems for your vehicle—from reduced fuel economy to serious engine damage. If you suspect that your MAF sensor is failing, have it checked out as soon as possible. Although it’s possible to drive with a bad sensor, it’s inadvisable, and ignoring the problem can lead to long-term damage to your engine that can be very costly to repair.

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