What I think could have killed my Mass Air Flow Sensor

cleven · Post by **cleven** » 13 Jun 2021, 20:35

After doing much reading I believe my Mass air flow has gone out on my v70. When i got the car it had this filter put on by the lady's Grandson a week before the trans went out. I drove it didnt pay any mind tell the last couple of HOT (99 degree) days here in Arkansas and the car been acting funny. I'm thinking sucking in all that hot engine killed the factory 400K Mass air flow. Getting a new Bosch sensor and actual lid so it can get air in how it should and hope for the best. Just wanted to share incase this happens to anyone else!

Post by **kcodyjr** » 13 Jun 2021, 20:48

Not likely. These things work by heating up a wire and then measuring the change in resistance as the air passing it cools that wire down.

Is that the kind of filter that has oil in it? If the kid overdid it, that could do in a MAF.

cleven · Post by **cleven** » 13 Jun 2021, 21:10

kcodyjr wrote: ↑13 Jun 2021, 20:48 Not likely. These things work by heating up a wire and then measuring the change in resistance as the air passing it cools that wire down.

Is that the kind of filter that has oil in it? If the kid overdid it, that could do in a MAF.

Yep oiled filter. I'm not a big fan of the open filter under hood thing but didn't pay to much mind to it. Iv always been under the impression on massairflow cars to use the dry type filter.

cleven · Post by **cleven** » 13 Jun 2021, 22:57

Going with a oil free filter. Going to hunt down a air box top tomorrow.

Post by **erikv11** » 14 Jun 2021, 07:43

cleven wrote: ↑13 Jun 2021, 20:35 ... the factory 400K Mass air flow ...

Congrats on getting the car to 400k. You must be doing something right! Or maybe it was just usage that wore out the sensor. Good move going Bosch on the replacement.

Post by **matthew1** » 14 Jun 2021, 11:32

Try hitting the MAF filament with MAF cleaner.

The air box lid should help intake temps. I never understood the open top stuff.

Azik09 · Post by **Azik09** » 14 Jun 2021, 13:48

These "zero resistance" filters are engine killers!
Dry filter just decreases air flow when clogged.
Oiled filter stops trapping dust when clogged...

cleven · Post by **cleven** » 14 Jun 2021, 14:23

matthew1 wrote: ↑14 Jun 2021, 11:32 Try hitting the MAF filament with MAF cleaner.

The air box lid should help intake temps. I never understood the open top stuff.

Yea tried cleaning it no go. I’m going to try another one today and hope for the best.

cleven · Post by **cleven** » 15 Jun 2021, 01:34

Well installed mass air flow sensor, cleaned ECM....... Went for a drive and bad idle and attempted stalling BUT no more ETM code

BUT a new one P1332

. Gotta say going from old 850’s to the P2 platform is a ROUGH transition. But I’m gonna stick to it. Oh and the new boost control is getting installed when it comes in tomorrow

. The 02 code has always been on the car because the old owner never had a 02 on the cat

EngineeringBloke · Post by **EngineeringBloke** » 15 Jun 2021, 14:22

The MAF has a pinkie sized sensor inside a 2-3 inch duct that is attached to the airfilter, on the engine side.

Inside that duct is a Bosch electronic sensor, roughly the size of your small finger.

The sensor has an external wired thermister that measures air intake temperature. However, the main work is done by a heated plate about a quarter the size of a small fingernail! The plate is inside the sensor and air is ducted through an S shaped tube within the sensor, next to a bypass tube. This design is intended to keep particles and droplets that have bypassed the air filter from contaminating or affecting the plate.

As air passes over the plate, the air cools and the sensor responds by applying more energy to heat plate back to its set temperature. This is measured and is used to determine the air mass going through the 2-3 inch duct to the engine. The reading from the thermister is used to compensate for the effect of the temperature of the air.

Due to the twisting of the sensor duct, I think that it is difficult to clean the sensor hot plate. But if the design resists cleaning with MAF cleaner, then it should avoid contamination from an oiled filter leaking oil droplets. So MAF cleaner is cheap enough and is not likely to harm the sensor.

As the sensor is held in the ducting with security screws, to access it for cleaning, you can break off the screw center pin and then use a suitable non-security bit or a flat blade, or just grip the screw from the side with pliers and rotate the screw slowly from the side.

Only use MAF cleaner as other cleaners will contaminate the hot plate.

I found the video on this page to be helpful in understanding the design: https://www.boschautoparts.com/en/auto/ ... 0281006110