A couple of months ago my car started throwing a long series of fault codes, and lighting up the SES light.
- 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.
1989 750iL 220k, but still runs great
2000 M5 128,000 miles. All mine. mine. mine.
2001 Tundra Hauls... stuff
2008 Z4 M Coupe My Roundel Cover Girl
2008 Mercedes C350 Sport wifey's car
2009 BMW R1200GS-Adv Rode to the Arctic Circle
2010 BMW G450X Dirt Bike with a Roundel
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.
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.
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
MY2001 Imola Red
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