Do you know the engine part in the image above? It’s called Mass Air Flow (MAF) sensor. This is an important component of how our vehicle’s engine functions. And sometimes, the MAF sensor can fail and cause your check engine light to come on or your engine to run like rubbish.
Today, we’ll discuss how important it is to keep the MAF sensor in tip-top shape and how to check if something is wrong with it.
What is a Mass Air Flow sensor?
Part of an electronic fuel injection(EFI) engine is a mass air flow, or MAF, sensor. Found between the air intake and the intake manifold, this device measures the amount of air entering the engine (or air flow).
You see, to maintain the optimal performance of an EFI engine, the internal computer of the vehicle computes the right mix of air and fuel inside the combustion chamber. Too much fuel, and affects fuel economy and leaves particles that mire the spark plugs. On the other hand, excess amount of air leads to rough idling, engine misfires, and car start failures.
How does the MAF sensor function?
There are two types of MAF sensors: the hot wire and the cold wire type. More common is the former, while the latter is used mainly on GM vehicles.
Hotwire MAF sensors function by using a constantly heated platinum wire in the middle of the device. When air enters the intake and passes through the sensor, the wire cools down a bit and this sends a signal to the computer to increase the voltage to heat up the wire again to its constant temperature of about 200-degrees Fahrenheit or 93-degrees Celsius. The readings here are sent to the car’s powertrain control module, which controls the fuel injection system of the vehicle.
The cold wire ones use “cold wires” together with hot wires to create the air flow readings to be fed to the ECU.
How to Clean the Mass Air Flow sensor?
Since the MAF sensor is constantly exposed to air particles and contaminants, it should be cleaned and maintained regularly. Here, we enumerate the steps to take to clean your MAF sensor:
- Make sure you turn off your vehicle.
- Unplug the sensor from its electronic connection.
- Remove the air intake tube and take out the MAF sensor.
- In a well-ventilated area, place the MAF sensor on a clean, flat surface.
- Using a special MAF sensor cleaner (which you can purchase from any automotive store), spray the interior and exterior of the housing, as well as the connectors outside.
- Be sure not to touch the hot wire and the plate as they are very sensitive. It may be a good idea to cover them before spraying the cleaning agent.
- Reinstall the entire system. Don’t start the engine right away, though. Allow the chemicals to evaporate.
Detecting problems with the MAF sensor
If you plan on skipping cleaning the MAF sensor, don’t. Not only are you sacrificing fuel efficiency and a comfortable ride, but you’re also risking damage to other parts of your vehicle due to the suboptimal air flow data received by the ECU. And did we mention the possible cost of additional issues if your vehicle experiences any MAF sensor-related problems?
Still, detecting a faulty MAF sensor can be tricky. But there are symptoms you can look out for:
- Stalls, hesitations, and sudden jerks while driving
- Hard starts
- Engine seizures and surges
- Rough idles
- Black smoke from emission
- Bad fuel economy
- Check engine light is on
- Car turns to limp mode
Air flow rate can also be tracked via an OBD2 basic diagnostic tool. Display this measure via your mobile device or head unit, so you can monitor your air flow while on the road. You can also detect MAF trouble codes via this device.
Another reason to get a handy scan tool? Once finished cleaning your MAF sensor, and you’ve repaired any problem in your car, you can clear the engine light and reset limp mode with this tool as well.
Testing your MAF Sensor
If you’re sensing something wrong with your MAF sensor, you can employ a basic digital multimeter (DMM) to test your sensor. Be sure, though, to consult your car’s manual to confirm the type of MAF sensor you have, as it may require a different type of DMM.
But before you try out any DMM to do MAF sensor testing, you can do these simple troubleshooting if you encounter any MAF sensor trouble symptoms.
Intermittent faults or poor idling
- While the engine is idle, engage the brakes and put your car into Neutral or Park.
- Open the hood.
- Give the MAF sensor and its electrical wiring a few gentle taps with a wrench or a screwdriver handle. Try wiggling the wires too.
- If the engine stalls or idle gets worse or better, then the MAF sensor is likely defective.
Poor starting or idling
- Open the hood and put your car into Neutral or Park. Engage the brakes.
- Unplug the connectors from the MAF sensor.
- Start the engine.
- If the engine starts or the idling gets better, then your MAF sensor needs replacing asap.
Testing the Mass Air Flow sensor Using a DMM
Newer vehicles today use a high-frequency MAF sensor. Therefore, they require a DMM or voltmeter that measures frequency. Otherwise, a simple digital multimeter is all that you’ll need.
Before doing the actual test, let the vehicle idle for about 15 minutes to warm up the engine. Then, turn off the engine, engage the brakes, put your car into Neutral or Park, and pop open the hood. Have your vehicle manual on hand so that you can readily compare the results of the tests.
To Test the Power Feed
- Unplug the MAF sensor electrical wiring
- Set the DMM to 20V DC or auto-range
- Connect the red wire from your DMM to the signal or “+” terminal of your MAF sensor. The black wire goes to the ground or “-” terminal (you may use your vehicle manual to confirm which wire is + and -).
- Turn the ignition to On, but do not start the engine.
- If you get lower than 10V or the ideal battery voltage, then you’ve got a power problem with the circuit.
To Test the Voltage Signal
- Plugin the electrical connector of the MAF sensor.
- Connect the positive and negative terminals of the meter to the sensor connectors.
- Start the engine and let the vehicle idle for a few minutes.
- The meter should display 0.5V to 0.7V, though some models may register a higher initial idle voltage.
- Gently tap the MAF sensor and its connections with a wrench or a screwdriver head. Give the connectors a slight jiggle.
- If the voltage fluctuates or the engine misfire or surges, this can mean a loose electrical connection inside the sensor.
- Rev up the engine to 2,500 to 3,500 RPM. The voltage should now read from 1.5V to 3V.
- If the reading becomes erratic or too low, then the hot wire inside the sensor may need cleaning because it’s dirty or contaminated. Meanwhile, no response from the sensor means you have to replace it.
To Test the Frequency Signal
- The electrical connector should be plugged in here.
- Set the DMM to the Frequency scale.
- Connect the meter’s red lead to the sensor’s positive terminal and the black lead to the ground terminal.
- Now, start the engine and let it idle. The ideal reading is 30 hertz (Hz)
- Do those gentle taps to the sensor and slight wiggles to the wires to check for loose electrical connections.
- Increase the RPM slowly.
- If the frequency is all over the place or is too low, there might be contamination of the hot wire or the circuit/relay. No reading means you need to replace the entire MAF sensor.
To Test the Hot Wire
- Unplug the MAF sensor’s electrical connector.
- Use the Ohms scale on your DMM.
- Connect your meter to the electrical connector. Make sure that the red lead connects to the positive terminal and the black lead to the negative terminal.
- An infinite resistance reading reveals damage to your hot wire or sensing element.
Our Final Word
We hope we have given you enough reasons to regularly clean that MAF sensor and monitor your mass air flow rate. Much like any other engine component, this component performs an important function. Thus, you need to start paying more attention to it.
And try to get quality yet affordable scan tools from a reliable source. Always, all the best for your car!