Car sensors are essential components in a vehicle. They help regulate certain functions or detect problems with different systems. They are like receptors. The mass airflow sensor is a critical part of the internal combustion engine.
Its primary role is to detect the air mass flow rate getting into the engine. The information helps the engine control unit to determine the fuel level supplied to the engine. It works effectively with an oxygen sensor for improved accuracy.
Looking at the significance of this car sensor, it is not surprising that many people want to know how it works. If you have the same concern, you are in the right place as we look at its working principle and signs of a bad mass airflow sensor.
What Is A Mass Air Flow Sensor?
A Mass Air Flow sensor is also known as an air meter. It plays a fundamental role in your vehicle. Namely, it measures the amount of air (mass flow of air) entering the internal combustion engine.
Based on these real-time inputs, the engine control unit estimates the amount of fuel mass needed to keep air and fuel in balance.
Additionally, note that air density changes with the temperature, pressure, humidity, etc. That is where, again, MAF sensors help. When it comes to measuring the intake air quantity in each cylinder, they are more precise than volumetric flow sensors.
What Does a Mass Air Flow Sensor Do?
As was mentioned, the MAF sensor measures the amount of air entering the engine. The PCM uses the MAF sensor signal when calculating how much fuel to give the engine—more air equals more fuel.
There are several different types of MAF sensors found in different vehicles. The two most common designs are hot wire and hot film. Both types of sensors operate in a similar manner.
To measure airflow, the PCM continuously provides electrical current to heat the hot wire or hot film element.
Airflow cools the element, reducing its electrical resistance, and creating an increase in current demand. The PCM uses the increase in current demand to determine the amount of air entering the engine.
It’s important to note that not all cars have a MAF sensor. Some models use what’s called a Speed Density System, instead. With this setup, the PCM uses input from the manifold absolute pressure (MAP) sensor and various other sensors when calculating fuel delivery.
MAF sensors can either be analog or digital. Some MAF sensors produce digital readings that change in frequency, depending on the amount of airflow that enters the sensor.
Meanwhile, other MAF sensors, such as those found in Ford, produce a DC voltage instead of frequency.
Which are the Other Types of Mass Air Flow Sensors?
Technically speaking, there are three additional MAF sensor types in use. Although less noticeable than a hot wire or vane-type sensor:
#1. Mass Air Flow Sensor of the Cold Wire Type.
These are often seen on the LS series of engines from General Motors. They function exactly like MAF “hot wire” sensors. But “cold wire” sensors have an extra resistor that senses the surrounding air.
This “cold” resistor provides additional information to the hot wire data and provides a more precise airflow measurement. Cold wire sensors need more upkeep to function properly, though.
#2. Mass Air Flow Sensor of the Membrane Type.
A thin electrical membrane has been inserted into the airflow in this instance. A thinner temperature sensor film that measures continuous temperature is applied to the top and bottom surfaces of the membrane.
As the current is used to measure airflow, it operates similarly to hot wire sensors in that regard. Membrane-type sensors are currently in the experimental stage.
Mass Airflow Sensor Problems
A MAF sensor suffers from a few problems when we start modifying an engine, and in some situations, they can become a real pain in the ass. These problems can include:
#1. Intake Restriction.
Since the MAF sensor must protrude into the airflow to do its job, there is a fairly good chance that it is also offering some level of restriction to airflow into the engine.
To make matters worse, the MAF sensor is often fitted with gauze or honeycomb screens to protect the sensor element and straighten the airflow.
Often it can be shown that the MAF really doesn’t cause any noticeable restriction, but in some cars, I’ve seen the removal of the MAF sensor show gains of 10 kW or more.
#2. Reversion problems.
One of the bigger problems with a MAF sensor comes when we fit a larger camshaft. At idle a large cam will normally offer that nice lumpy idle which lets everyone know you mean business.
This lumpy idle also results in air reversion where the intake air pulses in and out through the throttle body and MAF sensor.
The MAF sensor isn’t fussy about which way the air is flowing, and when a reversion pulse comes back out through the MAF sensor, this air movement is still measured.
What this means is that air which has already passed through the MAF sensor and has been measured gets measured for a second time as it exits the MAF.
This plays havoc with the tuning because the ECU now thinks more air is entering the engine and extra fuel is injected causing a very rich mixture, poor idle quality and erratic drivability.
A similar issue can occur when we slam the throttle in a turbocharged engine. Here one of two things will happen.
Either the blow off valve will open, venting all of the air that has already been metered by the MAF sensor straight out to atmosphere and causing the engine to run excessively rich.
Or if a BOV isn’t fitted or can’t vent the pressurized air, this air will all back up and exit back through the turbo and MAF sensor, again resulting in a rich mixture.
#3. MAF scaling.
Each MAF sensor is designed to measure a certain amount of airflow based around what the engineers expect an engine to require. At some point, the MAF sensor will become maxed out and no longer be able to measure additional airflow.
When this happens it becomes impossible to tune the engine correctly as the ECU doesn’t know that extra air is entering the engine.
While for mild and even moderate power upgrades this is unlikely to be an issue, if you are looking at serious power upgrades such as forced induction then you may find that you exceed the flow range of the MAF sensor.
#4. Physical size.
Many MAF sensors are reasonably bulky, and this bulky mass needs to be located somewhere in the intake system.
Obviously this is taken into consideration in a factory engine bay, but if you’re looking to add a turbo or supercharger, finding space for everything can become challenging in today’s modern engine bays.
Symptoms of a Bad Mass Airflow Sensor
How do you know if you have a faulty mass airflow sensor? The following are some of the symptoms that may indicate that this engine component is failing.
#1. Engine Throws A Code.
A common sign of a failing mass airflow sensor is when the engine throws a code via the check engine light.
When the check engine light goes on, it indicates that there is a problem requiring your attention. You can use an onboard diagnostics scanner to read the code from the engine control unit.
In the case of the MAF sensor, the code will be between P0100 to P0199. These codes indicate an issue with the fuel and air metering system. The affected part may be the mass airflow sensor or throttle body.
The most common codes that you will see if you have a problem with this sensor are P0101 and P0102.
The former code indicates that it is out of range or a general performance hitch. The latter code comes due to the sensor having a low voltage output. The underlying problem may be a clog due to the presence of foreign objects in the airway.
#2. Stalling And Struggling To Get Power.
If the engine is prone to stalling and struggling to get power, you may be having an issue with the sensor.
The issue at hand is that the engine is getting more air than fuel, leading to an improper air: fuel ratio. This situation mostly comes due to dirt building up on the sensor’s wires.
#3. Poor Fuel Economy.
The prominent role of the MAF sensor is to detect the airflow to the combustion chamber for the release of sufficient fuel.
If this part fails or stalls, it may send the wrong information to the ECU. Incorrect signals may lead to excess fuel release, and you may find yourself visiting the filling station more frequently.
#4. Excess Exhaust Fumes.
Another sign of a bad mass airflow sensor is the release of excess exhaust fumes. This comes from an incorrect air-fuel mixture, primarily due to the ECU receiving wrong signals from the sensor.
Black smoke from the exhaust means the vehicle uses too much fuel, possibly from the disproportionate air: fuel mixture in the combustion chamber. Additionally, you may notice a strong smell of fuel in the exhaust fumes.
Other symptoms of a poor MAF sensor are poor acceleration, engine knocking, and a rough idle. All come due to an imbalance of the air and fuel mixture.
#5. Mass Airflow Sensor Locations- Depending On Vehicle Model and Brand.
As a car owner or mechanic, you must know the location of the mass airflow sensor. As previously mentioned, you find this component between the air intake filter and the throttle body or intake manifold in most car models.
It lies on the air pathway for it to detect air density and temperature. You will realize that this part’s location varies depending on the vehicle model.
For instance, you will find that the mass airflow sensor BMW position is on the driver’s side. In this case, if you have a right-hand drive car, the sensor is on the right-hand side.
The same applies to a left-hand drive vehicle, where you get it on the left part of the engine.
For GM brands, like Chevrolet, the MAF sensor’s location is precise. It should be at least 10-inches from the throttle body. Its side closest to the filter and throttle body should be at least 3 and 1-inches, respectively, of straight.
Furthermore, you should mount it atop the intake tube at a 180-degree angle. The specifications make it more efficient and less prone to failure. The distance from the throttle body does away with impulses, which may affect the readings.
Causes of Mass Air Flow Sensor Failure
Unfortunately, just like all electronic devices such as smartphones, computers, or even your digital watch, things can go wrong.
#1. Contamination or Dirt Build-Up.
Over time, tiny dirt particles may escape the filter medium of an air filter and start to build up on the delicate MAF sensor element.
If we consider the sheer volume of air an engine sucks in over many years and miles of driving, there’s bound to be some dirt build-up that will cause issues.
#2. Electrical or Wiring Issues.
A loose connector on the MAF sensor will cause interrupted electronic signals to the ECU, or a frayed wire from the wiring loom rubbing in the engine bay will also cause incorrect readings. The connectors on the MAF’s small PC board may also be damaged or loose.
#3. Age and Wear Over Time.
With the huge volumes of air being sucked through the MAF, eventually, some wear and degradation of the delicate sensor element or PC board will happen.
How Is a Bad Mass Air Flow Sensor Diagnosed?
It’s relatively safe to continue driving for a while even if your mass air flow sensor is about to fail. However, you’ll have to put up with the previously described symptoms. In a nutshell, poor performance, jerky idling, high fuel consumption, etc.
In general, a broken MAF sensor wouldn’t immediately ruin your engine; instead, it would just compromise and make it uncomfortable to operate your car.
This should give you enough time to get it checked out at a mechanic. Nevertheless, we advocate immediate action and advise against delaying.
A bad sensor will make the engine run worse in the long term. Additionally, those symptoms would quickly speed up engine wear and tear if ignored for a long time. Later repairs will cost more as a result of this.
Diagnosing the MAF sensor is the first step in solving the problem if you notice that the engine is not running as smoothly as it once did. Before figuring out how much a mass air flow sensor costs, do the following actions to diagnose the issue:
Step 1: Use An OBD2 Scanner to Check for Error Codes.
Connecting an OBD diagnostics kit is the simplest way to determine what’s wrong with your car.
Your ECU is remarkably good at identifying even the smallest subtest of problems. This is beneficial because a malfunctioning MAF sensor is one of the most difficult parts to identify.
A single error code might identify the precise root cause of an underlying problem, potentially saving hours of diagnostic time.
This will speed up the procedure and maybe keep you from misdiagnosing any issues with your car. Look for any P01XX error codes to rule out a bad MAF sensor.
The air flow-related sensors such as the MAF, MAP, BARO, and other similar sensors, as well as those error codes between P0100 and P0199, are of particular interest. The most frequent ones associated with a defective MAF sensor include:
- Code P0100 – Volume or Mass moving air Circuit Failure
- Code P0101 – Volume or Mass moving air Problem with Circuit Range Performance
- Code P0102 – Volume or Mass Low Input Air Flow Circuit
- Code P0103 – Volume or Mass High input airflow circuit
- Code P0104 – Volume or Mass Intermittent Circuit for Air Flow
Be aware that more sophisticated OBD scanners and readers can let you view the MAF sensor values in real-time. RPM is typically used to quantify them. More air must pass through the MAF sensors as your RPMs (engine speed) increase.
The MAF sensor ought to read 0mg when you’re idling. Then, as the RPM increases, it rises steadily and gradually. Keep in mind that the airflow value must not change. It might increase to 3 mg at 1,000 RPM, 6 mg at 2,000 RPM, 9 mg at 3,000 RPM, and so forth.
Step 2: Be Sure to Visually Inspect the MAF Sensor.
You might visually examine the MAF sensor while you’re near the engine. Particularly, look at the wiring. Are the wires showing any rust or even any obvious evidence of damage? Including fraying, burns, short circuits, and other issues.
In addition, you ought to examine the sensor itself. Do you see any oily residue on it or any dirt or other debris accumulating close to the measurement elements?
Additionally, given the sensitivity of the measurement components, check to see if there is any drifting or damage there as well.
You can bench-test your MAF sensor with a multimeter once you’ve determined that it is to blame. This should help you determine whether the voltage output from the MAF sensor is consistent with how it should operate under typical conditions.
If those voltage measurements are abnormal or you observe that it fluctuates regularly, the MAF sensor is broken. Turning off the engine, putting the transmission in “Park,” and applying the handbrake are the first steps. After completing that, you can move on by:
Step 3: Utilizing a Multimeter to Test the Mass Air Flow Sensor.
- Find your car’s MAF sensor right now. It should be situated between the intake manifolds and the filter housing in the majority of vehicles. Others could discover that it is positioned just in front of the throttle body.
- If you want to know what range of voltage the MAF sensor should be operating at, you should consult a service handbook for the particular make and model of your automobile.
- Connect the black wire of the multimeter to the ground circuit and the red lead to the MAF sensor.
- You can now start the engine and let it idle.
- On most autos, the MAF sensor should read between 0.5 and 0.7 volts while the engine is idling. Once more, this will differ based on the brand, model, and features of your vehicle.
- Alternatively, you might use the screwdriver handle to lightly tap the MAF sensor. However, take care not to physically strike the exposed measuring components.
- The readings should stay constant with a short touch of the sensor when it is running at idle. Otherwise, any flux in the voltage values is a sign that the wire is broken.
- By revving the engine, you may also conduct a more thorough diagnosis. 2,500 to 3,000 RPM, let’s say. The MAF sensor will be taking in more air when the engine is running at this higher RPM.
- Look at the readings right now. It should show between 2.0 and 2.5 volts, which is significantly higher than idle (dependent on the vehicle).
- The entire sensor has failed if the voltage increases not at all.
- Try touching the measuring element with a multimeter that you already have while the ignition is off and the MAF sensor is unplugged.
- The leads should be placed against the hot wire element gently. If it displays infinite resistance (represented by the letters ‘OL’ in ohms), the hot wire is broken.
How to Clean a Mass Air Flow Sensor?
In some cases, you can clean the MAF sensor to restore normal performance. You can clean the device using a dedicated cleaner that comes in an aerosol can.
What You Need to Clean a Mass Air Flow Sensor?
The tools and supplies needed to clean a MAF sensor vary, depending on what type of car you have. But, in general, you’ll need:
- Clean towels
- MAF sensor cleaner
- Safety glasses
- Screwdriver
When cleaning the MAF sensor, you should always follow the instructions listed on the product you purchased. In general, however, the process involves the following:
Warning: Do not use MAF cleaner on Karman-Vortex style MAF sensors. This type of sensor uses either an ultrasonic receiver or a pressure sensor to detect vortexes in the airflow through the sensor.
Step-by-Step Instructions for Cleaning the MAF Sensor
1. Put on your safety glasses.
2. Locate the MAF sensor (positioned between the air filter assembly and throttle body).
3. Disconnect the MAF sensor electrical connector.
4. Use a screwdriver to loosen the clamps on the air intake duct.
5. Remove the MAF sensor by pulling it out of the air intake duct.
6. Place a clean towel under the MAF sensor.
7. Attach the straw to the aerosol can. Then spray the recommended amount of cleaner (as listed on the product instructions) onto the sensing element inside of the MAF housing.
Note: Do not allow the straw to contact the MAF sensing element.
8. Allow the MAF sensor to dry thoroughly.
9. Reinstall the MAF sensor into the air intake duct.
10. Use a screwdriver to tighten down the clamps on the air intake duct.
11. Reconnect the MAF electrical connector.
How to replace a faulty MAF sensor?
Once you’ve identified that the MAF sensor may be at fault, it’s best practice to follow these simple steps:
- To begin, connect a diagnostic tool to your vehicle. Select the correct make, model, year, and engine code of the vehicle you’re working on. Record the fault codes, and check the live data parameters for the MAF sensor. Then exit the diagnostic software and switch off the ignition.
- You’ll also need to check the feeds, ground, and wiring. Connect the oscilloscope. Ideally, a break out lead should be used to prevent puncturing the wiring’s insulation and causing a future wiring issue. To get a reading, snap the throttle open and observe the pattern.
- Once it’s determined that the MAF sensor is at fault, you’ll need to replace it. Remove the connector and then the fastening screws. Next, remove the sensor from its housing.
- Inspect the flow tube to ensure there are no cracks in the plastic housing. If there are, you will need to replace the entire unit – not just the probe. If the flow tube is crack-free, then you’re ok to replace the sensor probe only.
- Remember it’s important to handle the sensor connector only. Never touch the electronics as this may damage the sensor probe.
- Carefully slide the new sensor probe into the flow tube, then tighten the fasteners and replace the connector.
- Reconnect the diagnostic kit and delete any fault code(s). Run the engine, and recheck for any new fault codes. Exit the diagnostic software and switch off the ignition. Finally, check that the check engine light has been extinguished, then carry out a road test.
Can You Drive with a Bad Mass Air Flow Sensor?
Although in some cases, you may technically be able to continue driving with a bad MAF sensor, you should address the issue as soon as possible. A faulty MAF can damage other parts of your vehicle, such as the catalytic converter.
What’s more, some cars won’t even run when the MAF fails. In other instances, the engine will run but run poorly, making the vehicle difficult to drive.
How Much Does It Cost To Replace A Mass Airflow Sensor?
There are times that the MAF sensor is so badly off that the only solution is a replacement. Among the factors to consider are compatibility and price.
The latter is essential, mainly when you are working on a budget. The average cost for replacing this engine component is around $150 to $200, without labor. With labor, you will part with roughly $40.
FAQs.
Q: Can A Dirty Mass Airflow Sensor Cause Misfire?
An engine misfire comes about due to incomplete combustion in the cylinders. One of the reasons is an incorrect air-fuel mixture. This disproportionate mixture may come about due to the ECU receiving the wrong signals from the mass airflow sensor.
A dirty sensor will malfunction and send incorrect info to the engine control unit. To beat this problem, you have to clean this part regularly.
Q: What Happens If I Unplug The MAF Sensor?
The MAF sensor is essential to the engine when it comes to fuel regulation. Despite its significance, you can still drive your car if you unplug it. The vehicle’s performance will significantly improve if the sensor was bad.
Q: Can I Use Wd40 On MAF Sensor?
WD40 is the to-go cleaning agent for most vehicle parts, upholding its versatility. An exception to its diverse functionality is on the MAF sensor.
You should not use it on this engine part as it may leave deposits, further contributing to its degradation. A mass airflow sensor cleaner is the best option when maintaining this element.
Q: How Often Does A Mass Airflow Sensor Need To Be Replaced?
Replacement is a crucial maintenance practice that will boost your vehicle’s efficiency. The MAF sensor needs replacement every 20000-25000-miles.
At this point, it is much degraded and not able to work to its best, more so if you drive in rugged terrain. Getting a replacement will help the engine beat issues like knocking and poor fuel economy.
Final Word
Car sensors are like our body’s sensory organs, helping to detect problems and regulate variables like fuel consumption and emissions. In this article, we touch on the mass airflow sensor.
It is very significant in the internal combustion engine, where it plays a role in regulating fuel consumption.
If you are an automotive engineering enthusiast, this piece is a great asset, showing you how this sensor works. Follow it to the latter to have an upper edge should your vehicle’s MAF sensor fail.