TECH: Clean your MAF, don't replace! - BMW M5 Forum and M6 Forums

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Old 2nd September 2003, 06:10   #1
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TECH: Clean your MAF, don't replace!

If you are having Air-Fuel mixture problems... Clean your MAFs.

Here's How

A couple of months ago my car started throwing a long series of fault codes, and lighting up the SES light.



Symptoms:
- at full throttle, like passing another car on an uphill, the Beast would drop into a limp-home mode.
- when idling it would occasionally stall
- car misfired and ran rough

Well, my dealer charged me 2 hours labor to investigate, eventually finding a vacuum leak, and then reset the fault codes. Well, $200 bucks lighter, the car threw more fault codes on the way home.

They suspected I would need to replace both MAFs. Cost? $407 per MAF. Yikes! And they weren't even sure that would fix it.

Well, I've been out of warranty for over 10K miles, so I didn't really want them spending more of my money to experiment with a fix. On their dime? Sure. On mine? Thanks, I'll do the experimentation.

So I bought a new MAF ($274 by mail) and swapped it in. Bingo! No more stalling, and runs much better at full tilt!

Well, I thought to myself, a while back somebody mentioned on the board that the K&N filter's oil had fouled their MAFs. I don't use K&Ns, but I'm sure after 60k miles there's some dirt in there. So I figures I'd clean out the old one and swap it back in.

All clean, replaced on the car... and... It Runs Great!

Dirt is your enemy.

Careful cleaning is your best weapon.

My solution might not fix your problem. Your mileage may vary. Blah, blah, blah.
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Old 2nd September 2003, 06:19   #2
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Thanks alot for sharing
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Old 2nd September 2003, 06:29   #3
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Good stuff! Thanks for the instructions! Might not be a bad idea to clean them every 6 months or so I would guess.
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Old 2nd September 2003, 06:35   #4
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Don - GREAT JOB! I think you did everyone here a great service. Thanks for taking the time to document it so thoroughly! My MAFs were replaced (under warranty, fortunately) recently - and although my symptoms weren't as severe as yours, I also felt an improvement in performance - more power and smoother.

If I had known how easy it was I would have serviced them myself.

2 comments:

1) Simple Green is highly alkaline, and is known to cause corrosion when it isn't completely rinsed away. I think your idea to use the alcohol is sufficient, but I would caution people to be sure to do a thorough rinse - you want no traces of SG left around. I'd be willing to bet someone here with a strong background in chemistry or automotive science can recommend a better solvent.

2) Vaseline is usually a BAD lubricant for rubber parts. It is a petroleum product and can cause these parts to swell. You would be safer to use a silicone-based lubricant. You can get a tube that will last you the rest of your life at any swimming pool supply place - it is used for all the o-rings in pool filter systems.
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Old 2nd September 2003, 13:07   #5
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Pardon my ignorance, as items are often called something else in other countries, but what is simple green ?

Thanks for the great post and info.
I just had my both mafs replaced under warranty 3 weeks ago and yes the beast does go and pull much harder.
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Old 15th September 2003, 02:50   #6
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very informative on a topic that counts!!!! immediately after putting in the AA CAI and recleaining my K&N's one MAF sensor had gone bad on my 2000 with only 25K miles on it, but the dealership had replace it under warranty. I did suffer from the problems described. a couple weeks ago, the other one had gone bad, no symptoms, but a SES light did come on and off a week before....once again under warranty....but with the use of this post and the GREAT pics....this will solve the problem for most of us, especially if out of warranty!!!

Simple green is a good cleaner, but it does seem to have a tough residue on whatever its used on.....the alcohol is good as an afterwash to force a quick drying effect on the sensor.....maybe a strong but gentle dish soap would be a better cleaner...ie Dawn??

Greg, you are a GENIUS....i swear. I have only recently been able to post to the board, just been too busy, but occasionally before i would always view the topics especially before doing a mod, or giving up to the dealership.....you have a lot of real knowledge and we are fortunate to have you sharing this with us!! .....also, not to forget the other great contributions from the moderaters and the members!! together we make up an unbelieveable database of info on this great machine.


also, Greg, good luck and thanks for taking the time to do the detailed experiment with the UFM temp sensor.
Thanks to everyone

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Old 20th September 2003, 23:25   #7
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Louv just saved me some bucks!

Same BS runaround with the dealer. Just cleaned my MAFs as noted in the excellent instructions and the difference is night and day.

- cold start is MUCH smoother now, very little hesitation
- acceleration overall is smooth and strong again

Tampa_m5, you could not be more right about the value of this board.

allan
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Old 3rd October 2003, 17:13   #8
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Great Post

Guys,

I just love this kind of common sense information. A screw driver, some electrical contact cleaner, perhaps Simple Green and your done in half an hour. Cool .


That being said, I have had the K&N filters for 10,000 miles with no ill effects. Still, it doesn't hurt to know about this procedure and keep it for future reference.


Thanks guys,

MarkAttention moderators - I feel this thread needs to be perminantly placed in the best of threads.
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Old 28th October 2003, 22:18   #9
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Quote:
Originally posted by madmax
Pardon my ignorance, as items are often called something else in other countries, but what is simple green ?

simple green is a degreaser that is supposed to be biodegradebale
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Old 30th October 2003, 00:16   #10
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i read it....
i understood it...
i acknowledged it....
i did it.....

there's one thing left to do.... and that is...

GIVE U A BIG SMOOCH DON!!!

THANK YOU FOR SAVING US ALL THE TROUBLE OF DEALING WITH THE DEALERS and ofcourse saving us hundereds of dollars!

Thank You once again!
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