How do I open up the MAF?

[BigKriss]

I've taken it off and want to look inside. I want to adjust the spring. Do I take the black cover off? There are no screws and its sealed with sealant.

http://img176.imageshack.us/img176/6096/picture0099wm.jpg

[winfred]

the cover pops off with a little force, unless you know what you are doing and have a need for more/less fuel id leave the spring alone or atleast mark it's position so you can get back to normal. i put a 535 afm on my 325 to go with the overbored throttle body and headers and it took a while to get it right, basicly a couple hours with my snap on scanner doing a run and reading data and adjusting, it still aint perfect but it's good. a good cleaning of the trace with a nonresidual solvent can do wonders

[BigKriss]

thanks

[bahnstormer]

kris u have an AFM not a MAF...
http://paulaxford.com/bmw730i/index.htm
be super careful

[E34-520iSE]

So how & why do you need to adjust the AFM? What are the symptoms of a "slack" flap? Is it CO related?

Cheers,

Shaun

[bahnstormer]

AFM Adjustment



























Cost: none

Difficulty:

Time: 40min
http://www.bmwe34.net/E34main/Maintenance/Engine/Data/AFM_picture.jpg
Picture courtesy of Jr England - Procedure courtesy of Bill R.
Idle problems can be caused by an Air Flowmeter (therafter AFM) out of adjustment.
Don't attempt to adjust your AFM without an exhaust gas analyser.



Procedure
Hex wrench.
Exhaust gaz analyser.
1. With the engine off: check the throttle body butterfly gap. It have 0.002" gap with a feeler gauge at the bottom of the butterfly. Stick a 0.002" gauge in the open throttle plate, let the plate close with the gauge down at the bottom and see how much drag you get removing it. Set the gap with the throttle stop if needed.
2. Warm up the car then shut it off.
3. Disconnect the O2 sensor at the connection. (round black connector).
4. Restart the car and before the catalytic converter gets hot (which it won't with the car just idling) insert the gas analyser in the tailpipe.
5. Adjust the AFF screw the the allowable tolerances, from 0.2 to 1.2. Bill's car is setup to 0.9 to 1.0 and it seems to give a better idle. It also helps get ride of a slight hesitation when accelerating.

The AFM can be turned over to locate the screw then you can turn it back a little bit. (If you turn it completely, you won't be able to insert the hex wrench).
The screw controls how much air bypasses the flapper on the afm. By screwing it in, less air bypasses and it forces the flapper to move further sending a different signal to the dme. Turn the screw in to richen the mixture and out to lean it..

If you plan on doing it without a gaz analyser:
Gradually turn the adjusting screw in very small increments and wait about 30 seconds after wach adjustment to see what it does to the idle. Don't adjust it more than one turn in either direction.


thanks to >>
http://www.bmwe34.net/E34main/Maintenance/Engine/AFM%20Adjustment.htm

[E34-520iSE]

Thanks Bahnstormer, that's a good piece on info - will check mine out before MOT (inspection) time in November. Any thoughts about what the "adjustable wheel" inside the AFM meter does? How would you know if there was a problem with the AFM flap?

Cheers,

Shaun

[Ted K]

Winfred can you give more details about this? "a good cleaning of the trace with a nonresidual solvent can do wonders"
What is the trace?
Is gumout carb and choke cleaner a good noresidual solvent?

[Ted K]

What are some symptoms that you may need to do this?

[shogun]

AFM Adjustment for 'Big 6' (M30) Engines
Simple test and adjustment of the AFM for smoother running

http://members.roadfly.org/louielouie/AFM_adjustment.html

[bahnstormer]

what are your opinions on this POV (point of view) from my local indy?

i told him about the adjustments possible on the TPS and the AFM and
he said not to touch it. basically its someting that bmw sets and shouldnt
be touched... what do u all make of that idea?

[BigKriss]

I cleaned the intake path and the AFM with some metho , I didn't touch the AFM per Winfreds advice. There was a bit of **** (small traces of oil and dust I suppose) in there, not any more. No noticable difference though.