Another fuel economy rant - MAF i6

[Doru]

I take it the MAF for post 2001 e39 should be same for all i6? If so, here's the story: My mileage slumped this winter season, and reading through the forum I wasn't too concerned. There were quite a few "winter" fuel rants implying that it will affect economy. So long story short, my city economy went to about 12.2 - 12.8 l/100 km (I think it's around 16-17 mi/gal - my math could be off though). And on the Hi-way about 10.8 - 11 l/100Km (about 22 mi/gal) Which is horrible. I thought I should change the O2 (pre-cats) so I ordered them Car has 58 K miles. But I also had to leave for a long hi-way trip. So I cleaned the MAF.
This one is totally different from the v8. It's one piece, one side has a metallic mesh (the "intake"). The other side has a sort of plastic "guide" where you can spray the contact cleaner. I was not inspired enough to take pictures - thought it's a too easy job, everybody knows this - here are my findings:
To acces the MAF, undo hose clamp behind MAF (red arrow),
untitled1.JPG
then the hose clamp of the air box (air horn side - purple arrow). Take off bolt #10, then see green arrow: take off this bolt from the resonator. Pull off the bottom part of the air box (where it's hold in place by the air horn). Then, you can lift it up, so you can see below where the 2nd bolt is that holds the resonator in place. Take off that screw (dark red arrow - thin one).
untitled.JPG
Now the MAF comes off. You can spray from the back side. I also took a Q-tip and cleaned it, but PAY ATTENTION. THERE'S A HIDDEN THIN WIRE LIKE A FILAMENT, RIGHT BEHIND A PLASTIC GUARD. IT'S ORIENTATION IS VERTICAL.
Also, there is some sort of a mirror in that short tube. I don't know what it's doing, but it was dirty.
After i cleaned it, I put all back together in reversed order.

Filled the tank up, zeroed it, and did some city driving and a long road trip.
Here is what I have now: 10.2 l/100km city (I think it's better than 22 mi/gal) and 7.8 - 8.1 l/100Km (this is about 30-32 mi/gal).
Again sorry for not being inspired enough to take shots.

[jamesdc4]

I take it the MAF for post 2001 e39 should be same for all i6? If so, here's the story: My mileage slumped this winter season, and reading through the forum I wasn't too concerned. There were quite a few "winter" fuel rants implying that it will affect economy. So long story short, my city economy went to about 12.2 - 12.8 l/100 km (I think it's around 16-17 mi/gal - my math could be off though). And on the Hi-way about 10.8 - 11 l/100Km (about 22 mi/gal) Which is horrible. I thought I should change the O2 (pre-cats) so I ordered them Car has 58 K miles. But I also had to leave for a long hi-way trip. So I cleaned the MAF.
This one is totally different from the v8. It's one piece, one side has a metallic mesh (the "intake"). The other side has a sort of plastic "guide" where you can spray the contact cleaner. I was not inspired enough to take pictures - thought it's a too easy job, everybody knows this - here are my findings:
To acces the MAF, undo hose clamp behind MAF (red arrow),
untitled1.JPG
then the hose clamp of the air box (air horn side - purple arrow). Take off bolt #10, then see green arrow: take off this bolt from the resonator. Pull off the bottom part of the air box (where it's hold in place by the air horn). Then, you can lift it up, so you can see below where the 2nd bolt is that holds the resonator in place. Take off that screw (dark red arrow - thin one).
untitled.JPG
Now the MAF comes off. You can spray from the back side. I also took a Q-tip and cleaned it, but PAY ATTENTION. THERE'S A HIDDEN THIN WIRE LIKE A FILAMENT, RIGHT BEHIND A PLASTIC GUARD. IT'S ORIENTATION IS VERTICAL.
Also, there is some sort of a mirror in that short tube. I don't know what it's doing, but it was dirty.
After i cleaned it, I put all back together in reversed order.

Filled the tank up, zeroed it, and did some city driving and a long road trip.
Here is what I have now: 10.2 l/100km city (I think it's better than 22 mi/gal) and 7.8 - 8.1 l/100Km (this is about 30-32 mi/gal).
Again sorry for not being inspired enough to take shots.

Doru,

I think those diagrams work very well! That's quite an improvement. How many miles on your current MAF?

[Poolman]

Good post--I'm not sure what your talking about though on the tube that you discribed that has a mirror that you cleaned.... In your first pic--the part 7--notice the ribbed section--that part leads to the idle control valve--from time to time it needs cleaning --also the ribbed section of the boot can and will develop holes that can cause havoc on fuel mileage as well.--If you decide to buy another boot (18 bucks from the dealer) note that at the bootom of the boot is a ribb that juts out and will fit between two other ribs on the outside bottom of the throttle body--it's there like that to insure that everything is orentiated the correct way when putting it all back together right----be off on that and you'll have to tear it back down till you get it right--ask me how I know

[Doru]

Doru,

I think those diagrams work very well! That's quite an improvement. How many miles on your current MAF?

58k miles on the MAF

Good post--I'm not sure what your talking about though on the tube that you discribed that has a mirror that you cleaned.... In your first pic--the part 7--notice the ribbed section--that part leads to the idle control valve--from time to time it needs cleaning --also the ribbed section of the boot can and will develop holes that can cause havoc on fuel mileage as well.--If you decide to buy another boot (18 bucks from the dealer) note that at the bootom of the boot is a ribb that juts out and will fit between two other ribs on the outside bottom of the throttle body--it's there like that to insure that everything is orentiated the correct way when putting it all back together right----be off on that and you'll have to tear it back down till you get it right--ask me how I know

The "tube" that holds the MAF itself has a sort of mirror at the bottom I think. That one was dirty. Nobody mentioned anything about that, so I was taken by surprise - first I thought there was another opening in that plastic "tube" that holds the MAF. Then I realised that it has a mirror or a very shiny surface.
Not sure about the boot that can develop holes? That's a first for me, so the next time I will take a close look at that part too. How many miles is it good for? This is getting interesting trying to fit / orient boots the correct way?
Thanks Poolman for pointing this one out.

[porksoda]

i get about the same mileage and hasnt changed in a while... what did you used to get in city?

my avg between hwy and city ends up being about 500-530 km per 60-65litres.

[Doru]

i get about the same mileage and hasnt changed in a while... what did you used to get in city?

my avg between hwy and city ends up being about 500-530 km per 60-65litres.

Last year before the winter season, it was around 10.8 / 100km. Then it start dropping slowly to 12.8 / 100km. I'm back to what I had before

[Poolman]

The part I mentioned started to develop holes around 80k miles.

[Doru]

The part I mentioned started to develop holes around 80k miles.

Thanks for the heads-up. I'll keep this in mind.
So, basically, around that mileage, once the fuel economy starts dropping, this might be one of the culprits to look for? Any other symptoms?
Thanks

[quattro PETE]

Doru,

Thanks for the detailed instructions. By following them, I was finally able to get my MAF out and clean it. Over the last year my fuel economy has also decreased by a few mpg, so let's see if this makes any difference.

Also, there is some sort of a mirror in that short tube.

Yeah, I noticed it too. Very peculiar. I wonder what purpose it serves. Mine looked pretty clean so I didn't touch it as I did not want to mess anything up in the process.

[Doru]

Doru,

Thanks for the detailed instructions. By following them, I was finally able to get my MAF out and clean it. Over the last year my fuel economy has also decreased by a few mpg, so let's see if this makes any difference.


Yeah, I noticed it too. Very peculiar. I wonder what purpose it serves. Mine looked pretty clean so I didn't touch it as I did not want to mess anything up in the process.

To get a "good" read, the best thing to do is fill'er up and reset trip odometer & mpg computer.
And that "mirror" is still a mistery to me. Might have something to do with that huge price of this type of MAF. lol.

[Joeman892]

how do u reset the MPG computer? I am going thru some bad mpg and i want to figure it out and resetting the computer will save me time calculating the progress.

[rocketwagon]

how do u reset the MPG computer? I am going thru some bad mpg and i want to figure it out and resetting the computer will save me time calculating the progress.

While in the MPG display on the MID, push the button on the stalk (the one you use to switch between modes) and hold it in for about 3 seconds. The MPG will zero out, allowing you to start from scratch.

FWIW, my MPG is also much better since I replaced my MAF. I think it was slowly failing before I fried it.

[Joeman892]

ok thanks alot, i hope i dont have to relace my MAF.. i heard that we can use one from VW? or do we need BMW one.

[Doru]

VW MAF's only for the v8 folks. We lowlings i6 have to spend za big $$$ for the MAF

[rocketwagon]

VW MAF's only for the v8 folks. We lowlings i6 have to spend za big $$$ for the MAF

Not true! AutoZone carries a reman version of our I6 OEM MAF for $219, FTW. Takes them 1 day to order it, they don't carry it in the store, but they can and will get it for you. Saved me $125 from the lowest price I could find for a new one. There's a $75 core charge that you get back when you bring the bad one back. Plus there's a full no-questions-asked warranty, I think for 3 years.

[Joeman892]

wait so it would be 219$ - 75$ ??? when u bring them ure old MAF

[Paintballistic]

does that resonator serve any real purpose????

[rocketwagon]

wait so it would be 219$ - 75$ ??? when u bring them ure old MAF

$219 + $75 core charge, $294 total. Bring back the old MAF, they give you $75 cash.

[Doru]

So I live N of the border.........

[gtxragtop]

Please stick with the stuff designed to do the job. Here is an example product. Using something else or touching the wires with Q-tips can be very expensive. crcindustries.com makes such a cleaner.

[bsdhesi]

For Doru,

Since you changed the sensors and cleaned the MAF, I guess we won't know if it was the cleaning or the changing that caused the improvement, or a combination.