A dirty MAF can cause all kinds of issues, stuttering on acceleration, CELs, hard / no starts. Most recommend cleaning every 20k but there is a lot of debate around this. The MAF sensor is a very delicate part that does not like to be manhandled, so every time you take it out you do risk damaging it. So be careful and lets see if we can get that Subaru running a little smoother!
If cleaning does not seem to do the trick you can always install a new senor. Subaru Legacy New Mass Air Flow Sensor MAF 197408-0010 / 74-50040 / LNE1620CA / 5S2954 / 64-1790 / 1974080010 – (CROSS CHECK PART NUMBER)
|2 new screws – M4 by .7, About 1 Inch long ( Yours may be shorter depending on the intake you have )||$12.88|
|New O-ring – 28mm id x 32mm o.d. x 2mm thick||$7.14|
|Mass Air Flow Sensor Cleaner||$12.41|
I will be on top of the air duct between the air filter and throttle body, circled in blue here:
Disconnect the wiring harness, remove the two screws and carefully pull the MAF Sensor from the housing.
You can now spray it with CRC cleaner. Some prefer to spray the cleaner directly on the key areas, while other like to spray it into a plastic bag then put the MAF in the bag and shake it. No real evidence supporting either method works better so go with what you feel comfortable with. Just be careful NOT to touch the wires – just hold it by the part where the wiring harness was connected as shown below. The cleaner will evaporate in a few minutes; let it completely dry before reinstalling.
If the screws look worn or the 0-Ring is loose now is good time to swap them out.
Screw it down and re-connect the harness and you are good to go.