Cleaning Mass Airflow Sensor Instructions

1. Buy a can of MAF sensor cleaner. Do not use brake parts cleaner or throttle body cleaner.

2. Remove the wiring harness connector to the MAF sensor.

3. Remove the two screws that hold the MAF sensor to the air cleaner housing and remove the MAF sensor.

4. Look at the sensor to find the sensor wires and the ambient air temp bulb. Inspect the rubber O-ring that seals the sensor to the air cleaner housing.

5. Read and follow the MAF sensor cleaner instructions to clean off the sensor.

6. Reinstall the MAF sensor (making sure there are no air leaks in the air cleaner housing) and road test the car.

 

When should one suspect that the MAF sensor needs cleaning?

 

Over the time I had my Prius, I cleaned the MAF twice. Noticed no difference in fuel economy or behaviour

Perhaps if you sprayed TB cleaner down the TB without removing the MAF, you would coat the two hot wires and cause an immediate problem. Or if debris otherwise was introduced into the MAF barrel

Otherwise it should be fine

My FJ is different. Doesn't take long for deposits on either the TB or MAF. After visiting with some FJ owning friends in the Mesquite NV, Vegas, and St George UT area while down at the March CTIA convention in Vegas, I am now convinced that cold weather operation contributes to TB and MAF deposits

My friends down there know I make frequent contributions to the FJ forum on maintenance matters. So they had me help them change the spark plugs (FJ Cruisers made before 2010 have regular plugs that should be changed every 2 years or 30,000 miles), clean the TB and MAF

Even with early build '07 FJ's, their TB's and MAF's were spotless

After one winter, my TB blade has appreciable deposits and the MAF hot wires and IAT bulb also have deposits

I can tell when I have to clean the MAF on my FJ - the fuel economy plummets and the auto trans begins to shift weird. It also feels "sluggish"

It takes me under 1 minute to clean the MAF with CRC Mass Air Flow Cleaner. That instantly restores fuel economy and proper shift behaviour in my FJ

So unless you are experiencing problems, your MAF is probably ok.

Never ever try to clean the two hot wires with a q-tip as you will likely destroy the sensor

 

I would say that you would think about cleaning the MAF sensor if 1) your mpg is lower than normal or 2) the engine exhibits driveability problems such as lack of power.

I cleaned the MAF sensor recently for the first time on my 2004, at 110K miles. However, it didn't seem that the sensor needed cleaning as the temp bulb was amber, nice and clean, prior to my applying the cleaner. No change to engine performance or mpg after the cleaning, but there was nothing wrong with either.

In the past I had changed the engine air filter at 15K mile intervals, when the car was operated in southern CA where the air quality is not very good. Now that I live in a less-populated area it looks like the engine air filter will last for 30K miles, no problem.

I'm puzzled at reports from some Prius owners who do have dirty MAF sensors at relatively low odometer readings, and suspect that inadequate engine air filtration is the problem.

 

I would like to know what ambient temps those Prius are operated in. Yes, a defective air filter would result in a lot of deposits on the hot wires

But very cold weather operation, especially short trip, there is a lot of vapour introduced into the intake side. This is how PCV works. Maybe or maybe not the use of VVT to "simulate" an EGR valve also contributes to this

 

I cleaned the MAF sensor on my '06 Prius at 120k miles today, just for general preventative maintenance and curiosity. I followed the write up given by Patrick above.
First, I disconnected the electrical plug from the sensor and detached the cable from the clip holding it to the air filter box to allow me to move the cable out of the way.
Then, I made good use of a small ratcheting screwdriver (shown in one of the attached pictures below) to loosen the small Phillips screwdrivers holding the MAF sensor to the throttle body.
Once those screws were removed, I gently wiggled the sensor out. I took a photo of the sensing elements, which looked clean even before I cleaned them.
I used CRC Mass Air Flow Sensor Cleaner, which I bought at Advance Auto for $8 / 11oz. can. I sprayed the elements and the amber temperature sensor with a few blasts. The sensing elements looked the same after cleaning, but the top of the amber temp sensor was cleaner, as others have already noted.
I then reinstalled the sensor, connector and cable clip, and everything is working fine (just the same as it was before I cleaned it!). It's a pretty simple job obviously, but it satisfied my urge to tinker for a little while.

 

FYI to all, a dirty MAF is the most common cause of lean burn DTC P0171

 

Oh boy, have I got a story about MAF sensor tonight.

As some might know, my mpg is really given me concern lately.

Tonight, I took a look at my engine. My engine is really grimy that I wouldn't be surprised if it's a carcinogenic source of chimeric steampunk voodoo energy.

It took me a while to figure out how to pull the wiring, because I was afraid to damage the cord.

Next, I brought a lantern to the MAF sensor, and the screw placements were barely visible due to the dirt and grime.

I found that I couldn't use my trusty stubby screwdriver. I didn't seem to have a socket drive to fit my socket screw bit that was provided with my socket set.

Finally, I go to my micro precision screwdriver set and use my flexible extension bar. There! Got the first screw on top.

Then I'm picking the grime off the second bottom screw on the MAF sensor; and I realize that I don't see a "+" or "-" indentation.

I'm scratching my head, because I think the bottom screw looks like it has a hex for a head, because the top is smooth and flat.

There's still a lot of grime around the circumference of the screw head. And I think I have a suitable bit for my flexible bar to use.

I would post a picture. But I can't get a good angle for lighting.

 

^oh... nm.

that wasn't the ... yeah, nm