How to: Clean the MAF Sensor

I got this e-mail from snapon.com (snap on tools) thought everyone would like it.

Tech Tip: Clean the MAF

Application: 1990-1999 Ford, Lincoln, Mercury, Ford Truck with Mass-Air-Flow Sensor (MAF)

Symptoms: Lacks power, rough idle, surge, hesitation, ping/knock, MIL on with one or more of the following codes. OBD-I: 171, 172, 173, 175, 176, 177, 179, 181, 184, 185, 186, 187, 188, 189. OBD-II: P0171, P0172, P0174, P0175, P1130, P1131, P1132, P1150, P1151, P1152.

Theory: The MAF sensor uses very thin wires or filaments in the air-stream to "read" the amount of air entering the engine. If the PCM is being given an incorrect air flow reading, it won't be able to meter the correct amount of fuel. The PCM will "learn" of the incorrect fuel metering by the O2 sensor signals and try to compensate, but will eventually reach a point where drivability problems arise. Even on properly maintained vehicles, a coating will build up on the filaments and insulate them from the air passing by and cause an incorrect reading. Poor maintenance and paper "fuzz" from cheap air filters will cause the build up to occur sooner.

The Test: The quickest thing to do is hook up a scanner and watch MAF data. As a general rule, if the MAF voltage is over 1.1v at idle and/or the long-term-fuel-trim (LONGFT) is negative 12% or more, the MAF is in need of service.

The Fix: Remove the actual sensing part of the MAF from its housing and clean the filaments. To do this, unplug it and remove the tamper-proof-Torx screws. Carefully pull the sensor out. You will now be able to see the filaments. Even if they look shiny to the naked eye, there can still be a build-up on them. The safest way to clean them is Denatured-Alcohol and a swab. Never soak the sensor or spray anything directly on it. Wet the swab with the alcohol and gently rub the filaments on all exposed sides. After installing the MAF, disconnect the negative battery cable for 10 minutes minimum to clear the PCM's memory. Reconnect battery and test drive to re-learn PCM and to make sure the problems are gone.

Kieth,
Thanks for the heads up. I'm going to put a stick on this for awhile so everyone can see it.

No problem

Anyone have a good way to get those torx screws out?

Originally posted by ralphwiggum
Anyone have a good way to get those torx screws out?

Click to expand...

I got a tool to remove mine at Home Depot a couple of years ago. It cost less than $3.00 as I recall...

They are called security torx bits get them at any auto parts store

thanks guys!

can someone show me a picture of where the MAF is on the engine? im not good at engines

It is the metal piece on the passenger side of the engine compartment that is connected to the air box on one side and the intake tube on the other side. It has a harness with four wires (I believe) that connects to the top of it. It's very easy to spot and get to.

sweet thanks man

You should buy the tool from Snap-on because they were nice enough to give you the answer. Did I mention that I work for Snap-on.

what happens if you dont dissconect the batterey for ten mins?

if you dont disconnect the battery it will not clear the pcm, hense it learns. so there will be no change. if you clear it it will have to re learn whar the airl flow to fuel flow is and such. so it will run better

tech tip...take a small screwdriver and a small hammer and give those pins inside the security torx bolt a little bump to the side...they'll snap right off and then you never have to worry about them again. as far as I know there hasn't been too many mas' stolen.

Harbor Freight Tools sells a complete set of torx security bits which has the correct size. I was about $10 for the complete set last weekend..

~Mark

Just wondering if Rubbing alcohol the same as denatured alcohol?

The alcohols are not the same. You can typically find denatured alcohol in drug stores. The first time I ever bought it I search the store for about 15 min. with no success. I finally walked up to where the druggist was and told him I couldn't find it. He gave it to me from being the counter. When he saw my puzzled look he laughed and explained that they control it because some folks drink it!

I still have pining in spite of cleaning the sensor. It's very frustrating since I like this vehicle in every other way. I'm not sure mine will ever go away with 167,000 on the odometer. Nothing has worked so far although I've followed every tipo I've read.

Originally posted by Dennis Myers
You should buy the tool from Snap-on because they were nice enough to give you the answer. Did I mention that I work for Snap-on.

Click to expand...

Hmmm.. I used to buy snap-on and MAC tools.. here is my oppinion.. snap-on ratchets of now days are junk.. the old ones were kick ass.. but now the snap on dudes talk ya into spending a few bucks on trading your old one in on the new Supposedly better ratchet I had the long handle ratchet and every week I had to get it rebuilt I used to work at a polaris Dealer so my tools were my job and I used them all day everyday.. and I kept on wrecking this stupid ratchet ( and no pipes on the handle) screwdrivers of snap-on are great I liked them better then any of the others out there.. but my point is this.. just cause you pay alot for something like snap-on dont let that dude on the white van truck make you think its the best.. hehe

Anyone know how to remove that wax or plastic that is coating the one torx screw?

I just tried to clean the MAF and i ran into this problem, but im not sure how to get rid of wax/plastic and had to put everything back together...it's also getting dark here in NJ!

Don

Replaced the MAF sensor less than a year ago. Even if showing none of the 'symptoms' mentioned by Snap-On, should I still clean my MAF sensor on a regular basis? And if so...how often?