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Thread: Is this an accurate way of tuning AFM

  1. #1
    Join Date
    May 2014
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    Aurora,Co
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    1986 635csi 2001 530i

    Is this an accurate way of tuning AFM

    I have been having lots of trouble getting my 86 635 to pass smog ( way too rich ).99,000 miles

    I am probably going to test the cat next by using a vacuum test to see if it's clogged.

    In the meantime I tried this:
    Using a DMM I measured the output of the AFM at the output arm at idle (about 1000 RPM) Yes I know it's high

    Car warmed up, new O2 sensor hooked up, AFM screw turned out 4 1/2 turns.

    Tried to move teeth on AFM, tightening by 1 tooth did make voltage go down about .03 volts.
    Decent idle was at about 1.09 volts

    Anybody else ever try this, is this a waste of time?

    Thanks,
    Jim
    Attached Images Attached Images
    Last edited by e24mpwr; 05-09-2019 at 08:54 PM. Reason: code whackness

  2. #2
    Join Date
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    Hagerstown,MD
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    1984 Euro 635
    Have a look at the attached. May shed http://www.bimmerboard.com/members/d...justment_d.pdfsome light.
    '84 Euro 635
    '88 M6 (Gone but not forgotten)

  3. #3
    Join Date
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    Ouch EuroGeorge that link doesn't work.

  4. #4
    Join Date
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    MT View, HI
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    '80 733i , '76 2002
    Been needing to do this. Your theory seems sound, but the numbers don't jive with what I found online.

    http://members.roadfly.com/louieloui...djustment.html

    http://web.archive.org/web/200704020.../e34a/id6.html

    Haven't tried them on my '80, but interesting theory.

  5. #5
    Join Date
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    Quote Originally Posted by 86 shark View Post
    Ouch EuroGeorge that link doesn't work.
    It's a PDF file. Need to download.
    '84 Euro 635
    '88 M6 (Gone but not forgotten)

  6. #6
    Join Date
    Mar 2007
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    Troy, MI
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    85 M635CSi, 85 745i
    Has the car ever passed smog in Colorado (+5000 ft) ? If not, and adjusting the AFM spring tension doesn't get you in range (14-15's at idle and cruising, 12's at WOT ?) , then you might need to look at a switch inside the ECU (see pic below). Maybe others with experience setting up these cars for higher altitude can chime in on what is needed. Lee's car came out of Colorado and I think he had some fun getting it to run right at lower altitude.
    DME siwtch.jpg

    EDIT: Adding these in case they are helpful:
    EG1.JPG
    EG2.JPG
    Last edited by Cjarvis; 05-12-2019 at 11:13 AM. Reason: New info
    Craig in MI
    85 M635CSi / 85 745i

  7. #7
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    '86 M635/'10 Clubman
    Quote Originally Posted by Cjarvis View Post
    Has the car ever passed smog in Colorado (+5000 ft) ? If not, and adjusting the AFM spring tension doesn't get you in range (14-15's at idle and cruising, 12's at WOT ?) , then you might need to look at a switch inside the ECU (see pic below). Maybe others with experience setting up these cars for higher altitude can chime in on what is needed. Lee's car came out of Colorado and I think he had some fun getting it to run right at lower altitude.
    DME siwtch.jpg

    EDIT: Adding these in case they are helpful:
    EG1.JPG
    EG2.JPG
    He's still working on it... (the details have changed, but I still wonder if the AFM straight...)

    If you have some free time, I'll fly you here and stuff you full of good food and booze between sessions with the car...

  8. #8
    Join Date
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    85 M635CSi, 85 745i
    Quote Originally Posted by e24mpwr View Post
    He's still working on it... (the details have changed, but I still wonder if the AFM straight...)

    If you have some free time, I'll fly you here and stuff you full of good food and booze between sessions with the car...

    Now there is an offer! Timing is good. I could make it a MTB road trip.
    Craig in MI
    85 M635CSi / 85 745i

  9. #9
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    1986 635csi 2001 530i
    Thanks for the info guys.

    On the altitude question it passed smog for 6 years before this too rich problem.

    The altitude could also be why my fuel pressure is a steady 40 slightly less than the 3 bar42.6 that is standard.

  10. #10
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    1986 635csi 2001 530i
    Cjarvis,

    Good tip, today I will take the ECU out and apart and look for these switch positions.

    Great diagram of the switch positions.

    Where it says mixture adjustment percentage, should I be looking to decrease the percentage as the car is running rich?

    Thanks,
    Jim

  11. #11
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    Quote Originally Posted by 86 shark View Post
    Cjarvis,

    Good tip, today I will take the ECU out and apart and look for these switch positions.

    Great diagram of the switch positions.

    Where it says mixture adjustment percentage, should I be looking to decrease the percentage as the car is running rich?

    Thanks,
    Jim
    I took my ECU apart and of course it's an 059 which isn't listed.

    The 059 switch was at position 0 and I moved it to position 3.

    I had to use my smallest Torx bit ( sorry, size label fell off ) on it to fit the triangular position screw but I could feel the different positions.

  12. #12
    Join Date
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    Denver, Colorado
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    1985 535i, 1980 635CSi
    Since 059 isn't listed, I'll leave this here for you:

    It is used to adjust the
    fuel mixture and retard the ignition timing in case you need to use substandard fuel. Notice that it has eight numbered settings. Normally you'd keep it at setting zero.

    For the 535i (059 ECU):
    Setting 0: Mixture 0%, Timing 0
    Setting 1: Mixture +3.9%, Timing 0
    Setting 2: Mixture -3.9%, Timing 0
    Setting 3: Mixture -6.3%, Timing 0
    Setting 4: Mixture 0%, Timing -3.1
    Setting 5: Mixture +3.9%, Timing -3.1
    Setting 6: Mixture -3.9%, Timing -3.1
    Setting 7: Mixture -6.3%, Timing -3.1

  13. #13
    Join Date
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    Quote Originally Posted by 86 shark View Post
    I took my ECU apart and of course it's an 059 which isn't listed.

    The 059 switch was at position 0 and I moved it to position 3.

    I had to use my smallest Torx bit ( sorry, size label fell off ) on it to fit the triangular position screw but I could feel the different positions.
    Hey Jim, How did changing the switch position work for you? My guess is that since it was fine for six years before now, the ECU switch isn't the answer. Have you already ruled out the coolant temp sensor?
    Craig in MI
    85 M635CSi / 85 745i

  14. #14
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    1986 635csi 2001 530i
    OK, I have had trouble with my 86 635 USA auto passing smog too rich by a factor of 10.

    Went and had a new muffler and new cat converter installed, both needed.
    Down to smog place, failed by factor of 6, inspector suggested waiver.

    Played around with AFM again , did switch to position 3 on ECU.

    Down to waiver folks, great people and about 10 steps above Car Care Colorado.
    Older fellow said it passed by a mile and was actually running a bit too lean.
    Marked AFM spring and wrote down # of turns out on AFM air mix.
    Loosened spring by 1 notch and it's running great.

    This has been a 2 year battle and I don't know exactly what I did differently from previous tries.
    On 2nd CTS and they both ohmed out correctly and a warmed up engine runs poorly and fast when I disco the CTS now so I think that circuit is working correctly.

    I'm not sure the ECU adjustment did the trick, more likely I got lucky and hit the AFM adjustment just right or all the ground cleaning and contact spray eventually paid off.

    I'm still puzzled but now it's time to work on my 71 Johnson 50 outboard motor.

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