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MAF Sensor being held in a person's hand

MAF sensor. Used to measure the mass of air entering the engine. The signal is used to inject the correct amount of fuel

If your car is running badly or it is just not as smooth as it used to be your MAF sensor could well be the cause. This article shows how to clean mass air flow sensor

How does a Mass Air Flow Sensor (MAF) work?

A brief background on what a MAF does. A Mass Air Flow sensor measures the volume of air entering an engine. By passing a current through a wire and measuring the change of resistance of the wire the ECU can measure how much air is entering the engine at a given time.

Mass Air Flow Sensors are usually easy to locate and if they have done a lot of miles they could well benefit from being cleaned

Very simple, no moving parts and very reliable. You can read more information about Mass Air Flow sensors at Wikipedia here

Mass Air Flow Sensor Symptoms – Problems and Faults.

The symptoms of a dirty Mass Air Flow sensor are as follows.

Uneven idle
General rough running
Uneven idle
Engine Surging slightly when cruising at steady speed
Engine suddenly losing and regaining power at light throttle openings
Inaccurate air/fuel mixtures
Erratic behaviour, sometime car is okay, other days car is almost undriveable especially when hot but also when cold

Why clean a Mass Air Flow Sensor?

In my situation I suspected a Mass Airflow Sensor problem so I called around to get a price for a new replacement. First of all it was difficult to track one down and second of all, the price was over 400GBP. So I decided it was probably worth trying to clean the one I had.

How To Clean Mass Air Flow Sensor – Removing Original Sensor

The Mass Airflow Sensor is usually enclosed in a hard plastic housing. We need to remove the sensor itself from the housing. In this photo the sensor is old and the screws which hold the MAF sensor unit in the main housing had corroded. Pliers were needed to remove the screws

First of all you have to find your Mass Airflow Sensor.

The location will vary depending on your car but it is usually pretty obvious where it is. It is located somewhere in the engine’s intake system. Before the throttle body on normally aspirated cars and before the turbo (usually) on uh, turbo cars. When you have found it, remove the section of plastic that contains the sensor itself.

Once you have removed the section of the intake that holds the Mass Airflow Sensor you have to remove the sensor from the housing. Again this varies from car to car. In this case it was located with 2 screws. The head of the screws where severely corroded so a pair of pliers were necessary to remove them.

Once the screws were removed the sensor housing itself had to be pried away from the housing. On the G20/Primera the Mass Air flow Sensor looked to be glued to the tube section/housing, so a flat head screwdriver was needed to prise apart the two components.

Once you have the 2 pieces seperted you can see the 2 wires that make up the MAF sensor unit.

In this case the wires were completely black, it was a suprise the engine ran at all! This sensor had been on the car for over 200,000 miles so the amount of dirt build up is not suprising.

To show how dirty the Mass Airflow Sensor was, the lower wire is cleaned the top is not.

How to clean Mass Airflow Sensor

To clean the MAF I used acetone and cotton buds. Acetone does not leave any residue behind when it dries and it does not effect electrical components so it is perfect for this use.

Nothing special about the cotton buds.

Mass Airflow Sensor cleaning is very straight forward, simply soak the end of the cotton buds and wipe the wires. Be extremely careful when cleaning the wires, literally just use the weight of the cotton bud, simply rest the cotton bud on the sensor and turn it slowly.

No force is needed, the weight of the cotton bud on it’s own is enough to clean the wires.

Using the weight of the cotton bud only, this is more than enough force to clean the Mass Airflow Sensor wires

If you add anymore weight you will likely break the wires so be careful.

How To Clean Mass Air Flow Sensor – Reassembly

Once the wires are clean (in this case “clean” was judged to be when the wires were back to a silver colour), reassembly of the MAF sensor housing is obviously the reverse of disassembly.

Stainless steel allen screws replaced the old items

One thing to note on reassembly is that because the Mass Airflow Sensor unit itself was originally glued to the tube section/housing there was no gasket. To ensure there was an airtight seal I simply wrapped the join between the two parts with electrical tape. This was the quick and easy solution, if you want to do a professional job you could obviously sand down the glue on both surfaces to make them flat and re-glue them together.

Electrical tape wrapped around join between MAF sensor unit and main housing. This is to ensure an airtight seal

Because the original screws were unusable I replaced them with some stainless steel allen key headed screws.

The old corroded screws holding the Mass Airflow Flow sensor, these were replaced

One thing I should point out is that I don’t know if some Mass Airflow Sensors have a special coating. If so, using acetone may well remove any coating. All I can say is in the Infiniti G20/Nissan Primera GT with a Hitachi MAF case the car was transformed by using acetone and after 500 miles there is no reduction in engine smoothness so it appears everything is working perfectly.

I personally recommend acetone to clean the MAF sensor

How To Clean Mass Air Flow Sensor – YouTube videos

There appears to be many videos on You Tube showing you how to clean your Mass Air Flow sensor.

From the videos I have seen, none of them use cotton buds, they simply spray some substance on the sensor.

From my experience this is simply not enough to get rid of the dust and other deposits.

Second of all, a variety of products are used to spray the sensors. Personally, the only liquid I would recommend is acetone and not the acetone used for nail remover.

These are the cotton buds after they were used to clean the MAF wires. I am not convinced that simply spraying the wires with a fluid is enough to remove the dirt. As you can see the wires were completely coated in dirt and dust

How To Clean Mass Air Flow Sensor – Summary

So all in all a very simple procedure that has cured all the running problems the car was having so a highly recommended procedure to carry out on your car if you are experiencing similar problems.

Of course, if you are unsure about anything get your sensor professionally cleaned.

This article is based in the cleaning of a MAF sensor on an Infiniti G20/Nissan Primera GT with Hitachi MAF sensor

This page was last modified Nov 4, 2018 @ 10:38 pm

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