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DIY Mass Air Flow Sensor (MAFS) Clean

impee's DIY MAFS Clean for BMW 318i e46
How to Clean the Mass Air Flow Sensor yourself!

Difficulty Level: Easy

Approximate Time For This Project: 1 hour

Prices: Professional labour costs for MAFS clean - £35 (private) or £155 (BMW) - per hour X 0.5 hours

Electrical Contact Cleaner or a MAFS cleaner 1 £5.99
Screwdriver Flat head bit 1  
Socket Wrench + extension bar 1  
10mm Socket 1  
10mm Spanner   from your BMW car tool kit 1  

*prices correct at time of publication

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1) Assemble Your Kit + Notes

Below is the total kit I used. As you can see, there aren't many tools required for this job at all.

Clean Duration: The Mass Air Flow Sensor (MAFS) should be cleaned no sooner than every 20-30k miles.

Note: If your car is not exactly the same model as mine, please the sensor may be different and also attached differently.

A diagram of the Mass Aif Flow Sensor Part #1.

MAFS clean kit


2) Engine Cover - Removal

Remove the main big BMW cover (Intake Manifold) at the front of engine using this method:

1) Remove the 2 clips at the front - pull up and then out the small round black pins (expanding rivets) with a flat head screw driver

2) Un-clip the hook on the top left

3) Remove the large hose on the top right

BMW Engine Cover Removal


3) The Air Filter Housing, Intake Silencer

This is the housing for the Air Filter, the Intake Silencer. It is best to remove this to be able to get the MAFS out.
Use a 10mm Socket to open the 2 nuts.

Air Filter Housing


4) Wiring Plug - Detach

Press a small clip on the plug and pull of the Wiring Plug.

Air Filter Plug


5) Intake Hose - Removal

Loosen this screw with the Flat Head Screwdriver and then pull of the big hose, the Intake Hose.

Hose Pipe Clip


6) Intake Silencer - Removed

You can see the Intake Hose and Wiring Plug unplugged.

Also in this photo, see the arrow...this is pointing to the location where the Vacuum Hose fits - this is a thin black rubber pipe. As you can see in this photo, mine had come off, hence when you are putting everything back together, ensure you fit the Vacuum Hose back in!

Air Filter Housing Removed


7) Intake Silencer - Removed

The Intake Silencer removed.

Air Filter Housing removed


8) Removing Mass Air Flow Sensor (MAFS)

Use the 10mm Spanner to remove the 2 nuts. Then pull of this circular item, this is the Mass Air Flow (MAFS).

Air Filter Housing


9) Mass Air Flow Sensor - Dirty

The Mass Air Flow Sensor (MAFS) may may not appear to be very dirty, but trust me, it is.

The 2 small arrows at the bottom point to 2 security screws (which I did not have the bit for and could not remove) that hold release the MAFS. As I could not open them I cleaned the MAFS whilst it remained fitted. Spary lots of cleaner everywhere inside and specifically into the 3 long arrows, as they are the main sensor parts.

MAFS dirty


10) Mass Air Flow Sensor - Clean

It already looks a lot cleaner.

Let it dry before you fit it back, then if you want at the end, use a cold hair dryer to make sure it is dry.

MAFS clean


11) Re-assembly

Now work in reverse order following all the above steps.

Ensure you put back the Intake Hose, the Vacuum Hose and then tighten the Intake Hose clip and also plug back in the Wiring Plug.

Take the car for a test drive and you will notice it to be alot smoother and responsive than before.

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DIY BMW e46 Mass Air Flow Sensor (MAFS) clean by - impee

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