The MAF sensor is an important component in the engine management system that helps measure the amount of air entering the engine.
Can you drive with a bad mass air flow sensor? With a faulty mass air flow (MAF) sensor, you will still be able to drive but not for too long.
Besides, if you don’t fix the sensor soon, you will have a number of issues such as poor acceleration, reduced fuel efficiency, increased emissions, and even lack of power before and/or while driving. This may also cause the check engine light to come on.
We are here to help you understand more about the MAF sensor system, bad MAF symptoms and troubleshooting of the problem.
Symptoms of a Bad Mass Air Flow Sensor
Stalling during acceleration
The most common sign that indicates a bad MAF sensor is poor driveability such as engine jerking or stalling while accelerating. The reason behind this is that faulty sensors cause excessive deposited fuel in the combustion chambers that generates unlimited sparks.
This symptom can appear when your car is cruising down or accelerating in a street/highway and can cause serious accidents and injuries.
Rich or lean air fuel ratio
Maintaining the right air-fuel ratio is essential for a car engine to perform well. The MAF sensor measures the airflow and then signals the PCM to assess the quantity of fuel for injection in order to have an accurate air-fuel ratio.
A bad sensor can overestimate the airflow and send wrong information to the PCM (Powertrain Control Module), which then may inject more fuel accordingly. Due to this, fuel efficiency may decrease, the tailpipe may emit black smoke, and engine hesitation may occur while accelerating.
It can also underestimate the air taken by the air flow, which can lead the PCM delivering less fuel than the required amount. A lean air-fuel ratio can make your car difficult to start or cause rough idling.
Starting problems
A bad MAF sensor causes the engine to use more fuel for starting than idling because the engine control unit cannot command enough fuel injection to start the engine immediately.
Rough idling
Rough idling can be another sign of a faulty sensor because smooth idling requires the right amount of fuel supply to the engine.
Check engine light coming on
If you notice any of the signs mentioned above, you may find the check engine light turned on because it is the key indicator of a bad MAF sensor.
Why Do Maf Sensors Go Bad?
As MAF sensors are exposed to dirt, air, and oil vapors, as well as all types of combustion dirt and debris, contamination is the most common reason they become bad.
Different outer materials go through the sensor and contaminate the internal parts of the sensor. A dirty sensor will malfunction and cause sluggish performance, poor acceleration, or stalling of your car engine.
How to Find if You’re Dealing With a Bad Mass Air Flow Sensor?
Without any tools
If you think your MAF sensor is defective but there’s no scan tool handy, you can simply plug it out and look into it.
If the engine misfires or there are other driving issues, unplugging it makes the vehicle run better as the ECM has to use alternate readings from memory rather than the erroneous readings from the MAF sensor.
Engine still working when the sensor is unplugged hints the MAF sensor is bad. But remember that this test is not 100% accurate.
With the scan tool data
You can check if the sensor is bad using a scan tool in three different ways –
a) Compare the good readings at the full throttle
This test requires taking reference MAF sensor readings (grams/second, voltage for analog sensor, and frequency for digital sensor) at full throttle for the engine. We recommend that you search service manuals and forums for reference values.
When you have the reference values, comparison them with your findings. If there’s a great difference among the values then your sensor is bad.
b) Inspect the O2 sensor at full throttle
The O2 sensor reads the RICH condition at full throttle. If the sensor reads LEAN, this is a typical symptom of a dirty MAF sensor (note that this can also mean an issue related to the fuel delivery).
c) Check the short-and long-term fuel trim
A faulty mass air flow sensor gives normal fuel trim readings at idle and higher readings at higher RPMs. If there are high fuel trim numbers at idle, you may have a vacuum leak.
Sometimes, a dirty sensor overestimates airflow at idle because surface contamination increases the surface area and cools it faster. In this case, your fuel trim will show negative values at idle.
With an oscilloscope
a) For digital mass flow sensor
Test the signal frequencies at full throttle and idle, then compare the findings with the reference value. Anything lower than reference value would suggest a dirty sensor (8.5kHz frequency is considered a good value on a new GM) and no signal means it has completely failed.
But to be sure, check if the power to the sensor is 12V when the ignition is on and the engine is running. Finally, test the voltage drop on the sensor ground – the value should be under 100mV.
b) For analog mass flow sensor
Compare the signal wire‘s highest voltage at full throttle with the reference value. Anything under 4V indicates a dirty MAF.
How to Troubleshoot a Bad Mass Air Flow Sensor?
- Examine the connector to see if it fits and contacts properly
- Find out if the sensor is damaged
- Inspect if any of the sensor’s measuring parts are damaged
- Turn on the ignition and inspect the voltage supply. You can look into the circuit diagram and find the pin assignment. 7.5 -14 volts is the reference value
- Inspect the output voltage by turning on the engine. Check the circuit diagram if its mentioned value is 0-5 volts
- Examine the connectors between the MAF sensor and the disconnected control units. Consider checking the circuit diagram if needed. Reference value is close to 0 ohm
- Electronically test the sensor with an engine management controller. If there’s an issue, search for the error code in the control unit storage. The code can be found through a diagnostic unit
How to Clean a Dirty Mass Airflow Sensor?
Dirt in the airflow sensor causes malfunctions. You should clean the MAF after every 6 months or whenever changing the engine oil.
To clean the sensor, first take it out from your car very carefully because the wires are very fragile and small, breaking one will need a replacement. After plucking out, spray the MAF sensor cleaner 10-15 times onto the plate or wire.
You can also wash by putting it in a container filled with rubbing alcohol. Move the container gently until all the dirt and grime are washed away by the alcohol. After washing or cleaning, allow it to dry completely and then reinstall it in your car.
Clean if your sensor is a hot wire type but if it’s a hot film type then buy a new one.
Different Types of Mass Air Flow Sensors
The Karman Vortex
A bit similar to other sensors but differs in some areas as it forms a Vortex. The mirror and the photocoupler senses the Vortex and then the signal is transformed to power and transferred to the PCM.
Vane MAF sensor
Vane MAF, also known as airflow meter, generally uses the changing voltage signal to the PCM to calculate the volume of air. For transferring the signal or variable it uses the potentiometer.
Cold Wire MAF Sensor
This sensor uses a narrow metallic strip, which vibrates when air passes through. The changes in the vibration frequencies are delivered to the ECM as a signal
FAQs
Q. What’s the life expectancy of an MAF sensor?
Ans: MAF sensors don’t need preventive or regular maintenance. With little care once or twice a year they can last a long time.
2. When can I expect to have MAF sensor issues?
Ans: There’s no exact figures but after driving your car for 18-25 thousand miles, you can expect to have a bad mass airflow sensor.
3. Does the MAF sensor have mileage warranty?
Ans: They do not belong to vehicle parts that have mileage warranty.
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