DIY: Cleaning or replacing your MAF sensor! So fresh and so clean.
We often overlook many aspects of our vehicle until the damage has been done. One easy area of attention to help keep your ECU informed and your engine happy is the MAF (Mass air flow) sensor. This sensor unless your are tuned upon speed density, reads the volume of incoming air and sends the info to the ECU to allow for the proper amount of fueling to keep your air fuel ratio where it needs to be. At idle/cruising it should be stoichiometric which is 14.7:1. Without proper input to the ECU these calibrations will be off causing your engine to run either too rich or too lean, both having their caveats. Which can cause sputtering, misfires, poor fuel economy, etc.
For 04-07 Wrx’s and Sti’s this is a very easy task, and with many Subaru Maf’s are located right on top and very easy to get to. 15 mins will allow you to remove, clean or replace. As long as you don’t drop the two little screws…
What can you do as an owner to keep these in check and your engine running smoothly? Keeping tabs on your fuel trims via your tuning software or Cobb accessport and utilizing a wideband 02 sensor/gauge can show data that relates to your MAF operation. Above 14.7 is lean, below 14.7 is too rich for idle/cruising, this is an easy area to check first with the above gauges or an accessport. Oiled air filters are a common performance upgrade that can decrease the longevity of your MAF sensor and allow for more inaccurate readings, The oil can pass through the filter element and coat the delicate sensors.
You can clean your MAF at a given interval determined by your driving environments and driving style. I would say once a year is a good time frame to keep it clean, you really can’t over do it. If you wanted to do it with your oil changes it would be fine.
After doing a bit of reading trying to sort a issue out on my car I stumbled upon a thread about MAF sensor degradation. Overtime the air elements just won’t function like a new MAF, a few tuners stepped in with data logs of new MAFs vs old, showing with a little over 100k miles it might just be time to replace yours. A few other threads showed drivability concerns that were fixed by replacing a working but not as precise sensor. The MAF was still operating well enough to not cause a check engine light but drivability was compromised and a new MAF was a fix that most shops didn’t think of.
My STi is at 112k and after swapping a backup MAF into the car I saw massive changes within my fuel trims and AFRs. This prompted me to take the plunge and replace it. Just with my backup sensor installed I noted a much more stable idle and smoother boost transition, showing the older sensor was getting lazy or just plain inaccurate. Now on to the repair/replacement.
For this all we need is a screwdriver and a can of CRC MAF air flow cleaner or a replacement Denso sensor Crc MAF air flow cleaner is basically a fancier version of brake clean to help protect the very crucial and critical parts that make up your MAF. If you do not use the proper formulation you can easily damage your MAF and will need to replace it. I have used CRC MAF air flow cleaner for the last six years and it has always worked well in all of my Subarus.
With your hood open move to the passenger side of the car and locate your MAF sensor on top of your air box. With the two screws removed you will set them aside in a very safe place. Then lift the MAF out of the air box being careful to hold it by the square base and not touching any of the delicate areas used for sensing airflow.
You can now unclip the MAF sensor and carry it over to your work area to clean it out. The two areas you need to clean are the exposed wire (Air temperature sensor) you will see below in the image and up into the opening there are two hidden elements. As the air passes over these it can calibrate the proper airflow and when they have a slight amount of dust or dirt on them they can perform their job properly.
While waiting for the MAF to dry out you can take a look at the circular rubber seal that helps seal the MAF in while keeping dirt out. If this is torn, creased or worn, it is a good time to replace it. Head to your local hardware store and match it with something similar.
Now you can place it back into the airbox careful to not bump it on anything. Take both your screws and tighten them to allow the o-ring to seal up. Snap the wiring back in and double check that it is tightly clipped in and won’t fall out. Afterwards I like to reset my Ecu at this time, to help erase the old perimeters set by the MAF before it was cleaned or replaced.
Take a moment to let your car idle and make sure it is happy. Letting it warm up and driving around your neighborhood to checking that everything is fine. Then double check the connections at your work area and take off for a longer drive to make sure it is operating well.
Congrats you have cleaned or replaced your MAF sensor! That wasn’t too bad and your Ecu should be getting the most precision data it can. Which if it was off should help your fuel trims, miles per gallon and power. Another little known maintenance secret to keep your car running better.