WOW! AFM adjustment a must for everyone

[Jon in Richmond]

I finally went in and adjusted my afm (adjusting wiper track). If you have not done this, I would highly recommend it. This took care of all the little flat spots upon accelleration. Car feels brand new. Looking at the old tracks where the wiper used to make contact it was obvious why there was some hesitation.

Here is the web site with the adjustment procedure. I would recommend moving the wiper up the shaft (South) as in the third diagram. This will give you the best new contact area. You can bend the wiper down with your hand and put the bends in the halfway point by pushing on the bend point with your finger nail.

Link: http://frwilk.com/944dme/afm.htm

[pdx 528e]

I had the exact same experience doing this earlier this week. A definite must if you have any dead spots in your powerband. Also, its a good time to bench test the thing with a 9 volt battery and a multimeter, to see that it has smooth graduated voltage increases as you swing the flap open.

Mine had no where "North" to go, so I had to try South.

[Duke]

AFM............aint got no stinkin AFM. Whats a AFM. Is that like a TRS-80 computer or an 8-track?

[rlomba8204]

Hey, I know I am likely to get flak for this post, but recently I had some problems with my 535 that I thought were related to a malfunctioning air flow meter. After reviewing the various posts here about adjustment, I asked a couple of BMW shops (not dealers) that I know if they do such things, because I noticed all of the decals under the hood to the effect that "adjustment is not possible" etc. Well, both shops, which have been working on nothing but BMWs for 20 plus years for one shop, 5 plus years at the other (15 years at a dealership prior to opening own shop) said that you should NOT open the AFM to adjust it as it will invariably cause problems. Same with the ICV, etc. Adjusting those parts usually is only to mask a problem somewhere else.

Now, I know the folks here have had good luck doing it, probably because you are more mechanically inclined than the average person, but I wanted to post this information so that the casual DIY or board browser doesn't get the wrong idea that this is a recommended procedure. I think it probably is something to be done prior to chucking your old AFM as a last try sort of thing, and only for folks who regularly work on their cars and know the e28 beast and motronic fairly well.

I don't intend to start a controversy, as my post is aimed at the newer members here. Stated differently, I think there are different levels of expertise here, and I wanted to post this so some guy who just got an e28 thinks it is normal and routine to start playing with the AFM. That person will probably cause more harm than good by opening it up.

[Craig in Davis]

rlomba8204,

I agree, good to point out opening the AFM is not generally a good idea. However, I believe you misunderstood the original post. The original post didn't deal with adjustment as in recalibrating the AFM. Did you go to the link? The point is to reposition the wiper on the wiper track within the AFM to move it onto a clean virgin portion of the wiper track. Using a fresh portion of the wiper track can solve some running issues. There are other causes for running issues and those should be addressed first but in the end the AFM may be the problem. The link explains it much better than I can. If you think about it, the AFM's are 18 to 24 years old with a lot of miles on them. The wiper track wears and the result is less than optimal output to the ECU resulting in incorrect information about air flow and poor/less than optimal performance.

[Jon in Richmond]

Hey, I know I am likely to get flak for this post, but recently I had some problems with my 535 that I thought were related to a malfunctioning air flow meter. After reviewing the various posts here about adjustment, I asked a couple of BMW shops (not dealers) that I know if they do such things, because I noticed all of the decals under the hood to the effect that "adjustment is not possible" etc. Well, both shops, which have been working on nothing but BMWs for 20 plus years for one shop, 5 plus years at the other (15 years at a dealership prior to opening own shop) said that you should NOT open the AFM to adjust it as it will invariably cause problems. Same with the ICV, etc. Adjusting those parts usually is only to mask a problem somewhere else.

Now, I know the folks here have had good luck doing it, probably because you are more mechanically inclined than the average person, but I wanted to post this information so that the casual DIY or board browser doesn't get the wrong idea that this is a recommended procedure. I think it probably is something to be done prior to chucking your old AFM as a last try sort of thing, and only for folks who regularly work on their cars and know the e28 beast and motronic fairly well.

I don't intend to start a controversy, as my post is aimed at the newer members here. Stated differently, I think there are different levels of expertise here, and I wanted to post this so some guy who just got an e28 thinks it is normal and routine to start playing with the AFM. That person will probably cause more harm than good by opening it up.

Well, if you go into the afm blindly and think that you are going to do something that you have no idea about then you are asking for trouble. But, if you have detailed instructions on how to do something that has proven benefits then it's not a problem. As with anything, if you don't have reasonable confidence to your abilities you should not try it. If you don't know how to check the engine oil then you shouldn't pull just any dipstick under the hood thinking that you know what you are doing. To say that a shop, be it a dealer or Indy shop, says this or that is not always Gospel. Take it for what it's worth to you.

For the most part, people come onto forums like this to learn new things that they can do for themselves and save some hard earned $$$$. That's what makes places like this great. Hey, if you screw up your afm, you can pick one up for $50 or less.

[rlomba8204]

Yes, thank you for clarifying that. I knew it was about adjustment and I have actually adjusted a friend's AFM in his 635 to get a "fresh track." But I appreciate your point, as my post was not as clear as it should have been, as evidenced by your response. Indeed, it is helpful to point out that there is a difference between what the original poster was talking about and adjusting the AFM for richness, etc.

Jon in Richmond -- your point is taken. I don't lack confidence to do such things. But the point I was trying to make was directed not to you, but to some of the newer e28 enthusiasts who may not have the experience to do it right. Detailed instructions or not, there's a difference between "hands on" experience and reading a manual or similar. For a newbie, I still wouldn't recommend ripping into the AFM based on the fact that you have instructions in hand. Anything I have learned to do on my car that is tricky, typically I have walked through with someone who has done it before. For you, the instructions are enough because you have experience, I am guessing.

Regarding used AFMs, that's a very dicey proposition in my experience, unless you get one from someone say on the board. And most of the used ones are just as bad as the one in your car now. As far as the mechanics go, I see what you are saying, and maybe I am too deferential, but in general, if someone works on these cars for a living, and on average these shops have 10 to 15 cars a day in and out of the shop, I just think that their experience, combined with the factory training, makes them a more knowledgeable source than I am, and possibly more knowlegeable than the average owner-enthusiast. So while I wouldn't take it as gospel, I wouldn't dismiss it either. We have the benefit of being with a very knowledgeable and enthusiastic group, so it was just something I thought people should know about, and they are smart enough to decide for themselves. I think that's your point too.

At the end of it, I am happy to hear that your car is running so much better.

[Yellow2]

Thanks a TON for the link Jon. While all I will do is check resistances and Maybe bend that arm to ride on a new track, i think im going ot let it be as is. The link is very helpful though and I didnt not know exactly how my AFM worked. A great writeup. Should this go in the Tech FAQ section?

[Gene in NC]

Now that I know about the segmentation of the plate I will try to count the steps or flats that I feel in '85 535 accelleration. No question that I can feel at least four.

Is the degraded performance of the AFM caused by physical wear of the plate or by transfer of material ( contamination) between contacts and plate? If the latter, would cleaning with a good contact cleaner and or a treatment with Stabilant to improve "connectivity" improve operation enough to avoid the bending fix?

With bending, how is the contact force restored and how important is maintaining the original force?

[Rich Euro M5]

Now that I know about the segmentation of the plate I will try to count the steps or flats that I feel in '85 535 accelleration. No question that I can feel at least four.

Is the degraded performance of the AFM caused by physical wear of the plate or by transfer of material ( contamination) between contacts and plate? If the latter, would cleaning with a good contact cleaner and or a treatment with Stabilant to improve "connectivity" improve operation enough to avoid the bending fix?

With bending, how is the contact force restored and how important is maintaining the original force?

I believe the problem is a result of wear through of the carbon track. If you open your AFM you'll immediately see the tracks cut by the wiper contact into the carbon.

Rich

[robeyff]

AFM............aint got no stinkin AFM. Whats a AFM. Is that like a TRS-80 computer or an 8-track?

Go back inside, the heat's starting to f@#k with you - your paint's on the way. Temperature Today in Charleston:

98F, 100% humidity

Medical University of S.C. report issued today indicates that normal activity (walking) in 100% humidity with temps at 95F or greater results in a bodily fluid loss rate of at least 3/4 gallon per hour.

[pdx 528e]

With bending, how is the contact force restored and how important is maintaining the original force?

I would recommend doing this with a battery and a multimeter hooked up. Only push the "rotor" down far enough on its shaft to get a good constant voltage reading. I was getting lower voltages with the least wiper arm pressure, so I just lowered it a bit at a time until a sweep of the AFM yielded smooth voltage increases.

[Jon in Richmond]

With bending, how is the contact force restored and how important is maintaining the original force?

I would recommend doing this with a battery and a multimeter hooked up. Only push the "rotor" down far enough on its shaft to get a good constant voltage reading. I was getting lower voltages with the least wiper arm pressure, so I just lowered it a bit at a time until a sweep of the AFM yielded smooth voltage increases.

I wish I was good with a multimeter, but I just eyeballed mine. After bending the wiper, I moved it back and forth across the contact area checking to see that the new marks it left were consistent. A true hack job.

[C.R. Krieger]

Should this go in the Tech FAQ section?

Second that! Maybe somebody can ask about legally copying the information in the link (with proper attribution, of course) in case the source goes down.

[Yellow2]

Well I opened up both my AFM's and saw the grooved tracks and adjusted the arm to ride on a new pathway just North of the origional. Car idles the same and everything seems to be normal, but at least its a maintence thing that I can not worry about later. Thanks.

[BAVARIANUT]

BUMP
If this thread isn't on the Tec Faq. It should be...

[BAVARIANUT]

Bump, again. Techfaq please....

[KillerPM]

I did this procedure as well.

A+ the results are.

[BAVARIANUT]

I think mine needs it as well, because every once in a while it seems the car loses alittle power throughout the power band.

[ElGuappo]

I am looking to do this soon, when I am accelerating at 3/4 o rmore throttle I have dips in my powerband.
This is one thing I will be doing at least.

J3

[efreak]

Ok so I really want to do this to finish the tune up of my e28, I ran into one little problem.

I can't seem to get the black cover off. It looks like its just a press fit but prying has led m nowhere and I don't want to snap the thing into a million pieces. Any tips?

-Matt

[Shawn D.]

I can't seem to get the black cover off. It looks like its just a press fit but prying has led m nowhere and I don't want to snap the thing into a million pieces. Any tips?

It is glued on. You will need to pry with firm and steady pressure at a corner to start separating it -- I used a wide-bladed screwdriver. The cover will have to be glued back on with something that will not damage the interior components -- I used Permatex Ultra Copper silicone.

[BAVARIANUT]

What about RTV silicone,

[davem]

Ultra Copper is just a type of RTV (room temperature vulcanizing) silicone. Permatex makes different "colors" for various applications.

[KillerPM]

Yah, the cover was a bit of a bitch to get off.

I "glued" mine back on with windshield silicone.