E39 M5, The Car that God Would Hate
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Marcus Brody
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PostPosted: Mon May 20, 2013 8:26 pm    Post subject: E39 M5, The Car that God Would Hate Reply with quote

MAFs on the E39 M5 really are a major culprit in any performance issues, and one (or two) that is truly knackered would reduce performance significantly.

There is a very simple way of testing it, as it should flow with 130 l/h or above if the MAFs is new:

First unlock the OBD:

1. Put your ignition to level II.

2. Push the right button. Hold it pushed in. Don't release it! Your display will change from whatever it showed before (That should be: Check Control OK) to: Test No.1

When it says: Test No.1

3. Push the left button (short push, like a mouse click). It should show your Car ID. (last seven digits of it, 2 letters and 5 numbers). You gotta add those five numbers up (e.g. DW57384 = 5+7+3+8+4 = 27)

4. Push right button till Test No.19 shows in the Display

5. Push left button as often as the number is you got (in my example 27times). The display should show 27!

6. Push right button again

Now that the OBD is unlocked, you should go to

TEST-NR. 04
VBR: xx.x L/100KM (mileage)

push one more time on the left button to get to the second part of TEST 4:

VBR: x.x L/HR (fuel consumption in liters/hr)

This gives you the flow rates, and if yours is down to 80-100 l/h it would explain the symptoms.

Also, you could try to disconnect both MAFs (simply unplug the cables) and if it runs better without, then the MAFs are knackered! I have a couple of MAFs lying around with 15-20.000 kms on them that I would be happy to "sell" cheap, if you need them.
http://www.pistonheads.com/gassing/topic.asp?h=8&t=749017&d=0&nmt=



^Just for future reference. Thanks, John.
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Marcus Brody
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PostPosted: Tue May 21, 2013 4:07 pm    Post subject: Reply with quote

Aaaaaand time for new MAFs. Ran through 2nd and 3rd twice, never saw anything over 80l/h. By all reports, this should also make the car noticeably quicker. Very Happy
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Raptor
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PostPosted: Tue May 21, 2013 4:23 pm    Post subject: Reply with quote

Yeah, that sounds pretty damning from what I've read today too.
I verified that there is a failsafe map that is used with the mafs disconnected. From what I read you should see more like 150l/h+ on that.

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Marcus Brody
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PostPosted: Tue May 21, 2013 4:29 pm    Post subject: Reply with quote

I pulled the actual sensors and gave them a much more thorough cleaning than the last time. I'll see what that does.

I'm thinking if I don't push the car super hard, it should still be fine to go to Pittsburgh on Thursday. Thoughts?
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Raptor
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PostPosted: Tue May 21, 2013 4:33 pm    Post subject: Reply with quote

I agree. It might be a little odd, but out of heavy load this likely a minor issue. I also didn't read about anyone claiming damage during normal driving either, just the obvious power loss.
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Buck Futter
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PostPosted: Tue May 21, 2013 6:28 pm    Post subject: Reply with quote

well at least that doesn't appear to be a super huge price tag in terms of BMW prices. I just looked it up and found a set of Bosch MAFs for like $300. on the grand scale of things, that's not too bad. but at least you figured it out!
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Marcus Brody
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PostPosted: Tue May 21, 2013 9:40 pm    Post subject: Reply with quote

$300 is a little better than I've been seeing. Where were those?
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Marcus Brody
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PostPosted: Wed May 22, 2013 4:19 pm    Post subject: Reply with quote

Unplugged MAFs, got 148.something l/h in 2nd and 3rd. Confirmation enough for me.


I think it is a bit faster. Triggered traction control on the stretch between the golf course and the bar...in third...in a straight line...on dry roads. Razz
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Raptor
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PostPosted: Wed May 22, 2013 4:24 pm    Post subject: Reply with quote

Sounds about right. Now buy some Mafs. I'll still be happy to throw something at them for the taxi service.
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Marcus Brody
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PostPosted: Wed May 22, 2013 4:39 pm    Post subject: Reply with quote

Gotta admit, I'm tempted to see what effect my cleaning had. Also came across this:



I used the spray but didn't touch the wires with anything. I've even heard of people taking light sandpaper to the wires (not that I'd go that far), so the paintbrush thing sort of makes me want to give it a try.
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Raptor
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PostPosted: Wed May 22, 2013 4:42 pm    Post subject: Reply with quote

If you're about to buy new ones anyway, what's the harm?
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Buck Futter
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PostPosted: Wed May 22, 2013 5:04 pm    Post subject: Reply with quote

proper electrical resistance would be required. so sanding the electrodes might not be a terrible idea. they're more than likely corroded or at least have a penumbra on them. sanding might be a great idea for something like that.
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Marcus Brody
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PostPosted: Thu May 23, 2013 11:15 pm    Post subject: Reply with quote

Hmm. Maybe I need some kind of soft scrubbing sponge material for this. Something that can get around the wire without beating on it too badly.
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Buck Futter
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PostPosted: Fri May 24, 2013 12:31 am    Post subject: Reply with quote

Marcus Brody wrote:
Hmm. Maybe I need some kind of soft scrubbing sponge material for this. Something that can get around the wire without beating on it too badly.


Emory cloth? Maybe acid treat it with strips of an old t shirt?

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Marcus Brody
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PostPosted: Fri Jun 28, 2013 1:06 pm    Post subject: Reply with quote

Used a nylon-bristle paintbrush, which probably wasn't 100% ideal because the edges of the bristles were possibly too smooth, but it bought me about 25-30 l/h. The car doesn't seem to want to go into protection mode any more either.
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