How to clean the mass air flow sensor??

Easiest DIY you'll ever do in your life, unless you have a kit that has the maf housing near the brake ducts which then require you remove the bumper or headlight..(headlight)


cant miss it.


66k views and counting in the fi forum.

Thanks MachRc

Originally Posted by Acarder

Why does this thread have like, ten thousand views and 15 replies

I'm definitely one of these people. I'll try this tonight and hope my car never goes back into Limp Mode.

Would a dirty MAF cause a P0171 or P0172 code error? I just tried to smog my car and it didn't pass the functional test because of these errors. I had one of the tubes at the MAF replaced about a year ago so I'm wondering if this is related. The car has been idling rough for a while (it sounds like it wants to turn off every few seconds but it keeps running). That characteristic corresponds to the check engine light that turned on around the same time.

To answer my own question: No
Cleaning the MAF sensor did nothing to fix the problem

First, this is a great thread....so I'm posting!! Got the CAF cleaner from Autozone and am going at it tomorrow.
On the way out the counter clerks says cleaning doesn't fix it. It is only temporary. I am fine with cleaning it all the time. However, when, if ever, would you need a new replacement vs. cleaning? How right/wrong was this guy?

Thanks,

HiD

Originally Posted by Tazlord

To answer my own question: No
Cleaning the MAF sensor did nothing to fix the problem

But did it have other positive impacts on the vehicle? If so what?

A few suggestions if you dont like the oiled filters switch to an AEM dryflow filter.

Also DO NOT use any abrasive cleaner like carb cleaner or brake cleaner. If you can't find the electrical MAF cleaner from CRC. Go to any electronics store or even some supermarkets will have am Electric Contact Cleaner.

Make sure the MAF is cooled down before you use it. As if you just got out of the car the hotwire type MAFS can still be well hot and it will damage the sensor if you use the cleaner and it cools it too quickly.

Originally Posted by RNLD66

For the first time I went for a test drive the other day and when I accelerate to about 2000 rpm, the car wants to die and then it kicks back in at 1000 rpm. Now if I accelerate slowly it will get up to about 3500 rpm. Also the engine light is on. Although when I disconnect the MAF plug it accelerates fine. I am going to try your advice about cleaning it with the MAF cleaner and see if that does the trick.

I had exactly this problem. Firstly it would die if I fully pressed the pedal, but recovered if I backed off a little. Then it progressed to virtually being undriveable. (Explanation:- this is a 318i with the M43TU19 engine.)

My first thought was fuel filter (as Fuel pump had been replaced just before I bought the car). This was no improvement, but a good move anyway.

Finding this thread/post I disconnected the MAF and it accelerated cleanly so this must be the area to concentrate on.

Bought some CRC MAF Sensor cleaner and gave it a clean from both the gauze end and the other end too. No Better

Further searching I realised the sensor was not the same as shown in Post #24 of this thread. The research I found suggested disassembling the sensor from the MAF and cleaning properly. Mine looks like this:-



I liberally sprayed the Thermistor, The Top Airflow port (which has a shiny plate inside) and Lower Airflow port ( which has three wires inside).

After letting dry (temperature in Melbourne, Aust today 40ºC !!!) and refitting, the car has never pulled more strongly, revving right out with NO hesitation and clean all the way. Thanks to all on this thread and forum as alternative was to buy a new Bosch unit from Clickable for $259. (The 318i uses a Bosch MAF, not Siemans as on the 325i)

Shoot I just noticed I said the same thing one post above this haha.

Originally Posted by TitanSilverE46

Further searching I realised the sensor was not the same as shown in Post #24 of this thread. The research I found suggested disassembling the sensor from the MAF and cleaning properly. Mine looks like this:-

Attachment 484538

I have an 2004 M3 and I have the same MAF as you do Titan. I followed the same procedure as you did and had similar results.

Hey guys. I've been running without the MAF sensor for about 6 months because after completely overhauling my cooling system I couldn't afford the $400 for a new one & the sensor was causing my car to stall out immediately after starting. I did buy the CRC MAF cleaner, no dice tho. I.e. the sensor is shot.

My question is, what are the ramifications of running without it? I've been told that gas mileage will suffer heavily, however, 6,000 miles later the drop-off has been negligible - practically imperceptible. What I really want to know are actual mechanical problems this could cause(not fuel efficiency or performance because in my experience neither of those were significantly impacted)?

One last question - I read somewhere that after cleaning the sensor I should have disconnected the battery for a bit to reset the computer because it didn't know to correct the mixture after running the car with the sensor disconnected - any truth to this? I'm going to try it out tomorrow, but figured you guys would know if that was BS or not.

Anyone know where I could pick up a new sensor for a reasonable price? Looking to sell my car and would like to get this fixed beforehand, if I can afford it.

Thanks!

Originally Posted by nikmorris47

One last question - I read somewhere that after cleaning the sensor I should have disconnected the battery for a bit to reset the computer because it didn't know to correct the mixture after running the car with the sensor disconnected - any truth to this? I'm going to try it out tomorrow, but figured you guys would know if that was BS or not.

Thanks!

I didn't disconnect the battery and the results were immediate.

Originally Posted by TitanSilverE46

I had exactly this problem. Firstly it would die if I fully pressed the pedal, but recovered if I backed off a little. Then it progressed to virtually being undriveable. (Explanation:- this is a 318i with the M43TU19 engine.)

My first thought was fuel filter (as Fuel pump had been replaced just before I bought the car). This was no improvement, but a good move anyway.

Finding this thread/post I disconnected the MAF and it accelerated cleanly so this must be the area to concentrate on.

Bought some CRC MAF Sensor cleaner and gave it a clean from both the gauze end and the other end too. No Better

Further searching I realised the sensor was not the same as shown in Post #24 of this thread. The research I found suggested disassembling the sensor from the MAF and cleaning properly. Mine looks like this:-

Attachment 484538

I liberally sprayed the Thermistor, The Top Airflow port (which has a shiny plate inside) and Lower Airflow port ( which has three wires inside).

After letting dry (temperature in Melbourne, Aust today 40ºC !!!) and refitting, the car has never pulled more strongly, revving right out with NO hesitation and clean all the way. Thanks to all on this thread and forum as alternative was to buy a new Bosch unit from Clickable for $259. (The 318i uses a Bosch MAF, not Siemans as on the 325i)

Just tried this on mine plugged the MAF back in and it runs terrible just as before. It's almost un drivable once the MAF's plugged in as soon as I unplug it she runs great

Originally Posted by Jimbow

Just tried this on mine plugged the MAF back in and it runs terrible just as before. It's almost un drivable once the MAF's plugged in as soon as I unplug it she runs great

time for a new mass airflow sensor.

Originally Posted by MachRc

time for a new mass airflow sensor.

Think it's what I'm going have to do because there's no vacuum leaks and everything else seems fine.

Can you spray the cleaner in both directions to clean the MAF? A guy at Napa told me to only spray it in the direction of airflow indicated by the arrow on the MAF. I'm sure it wouldn't hurt to be more careful rather than not, but I also want to get that bitch clean!