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Thread: MAF Hack and Running Terribly

  1. #26
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    just to confirm the obvious - miller performance has indeed shut down. their web page can still seem to take your money though...

  2. #27
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    So the Bosch MAF came and it has 5 pins, not 4. And a different connector type.

    Any advice on sending this one back or trying to find out what the pins are for and see if I can match those up with the 4 on my old MAF? Or keep looking?

    Here is a picture of the new one.
    IMG_2499.jpg
    And the one in my e30:
    IMG_2492.jpg
    Last edited by LongTallTexan; 05-22-2023 at 06:59 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  3. #28
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    These are the readings I get with my multimeter for the Miller MAF conversion.
    Screen Shot 2023-05-22 at 8.13.22 PM.jpg
    I understand the 5th pin is for intake temperature (which this modification does not use).
    Last edited by LongTallTexan; 05-22-2023 at 09:22 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  4. #29
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    I think the Bosch MAF I have is this one for VW/Audi applications:

    Attachment 715970

    Wiring is (from left to right):
    Pin 5 - MAF Signal
    Pin 4 - 5 volt reference
    Pin 3 - Ground
    Pin 2 - 12 volt source.
    Pin 5 - Intake air temperature, not used.

    Not sure how to confirm this, but for $70, I guess I have the parts to give it a try!
    Screen Shot 2023-05-22 at 8.29.54 PM.png

    - - - Updated - - -

    maybe this is the pigtail I need?

    https://www.amazon.com/Sensor-Connec.../dp/B01EELKTEW

    But how to confirm the pinout on the 5-pin MAF?
    Last edited by LongTallTexan; 05-23-2023 at 12:13 AM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  5. #30
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    Saw a youtube video that said if you unplug the MAF while your engine is running, and the engine dies, that means the MAF is good. Any truth? Mine dies when that is done.

    And the Bosch MAF element has F00C2G2040 part number on it. That doesn't give me 4-pin elements!
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  6. #31
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    i'd see if you can swap the connector over. it's just two screws.

  7. #32
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    Quote Originally Posted by 82eye View Post
    i'd see if you can swap the connector over. it's just two screws.
    The two screws secure the MAF sensor to the housing.

    There is a fitting for the connector type that snaps on.

    And you can see a part number on the sensor, but even with that I can't find a 4-pin to buy.

    I have to figure that the calibration of these are identical - why would Bosch go to the expense not to standardize the sensor even if the housings are different.

    My dilemma is to know the pinouts the 5-pins so I can wire it up. (I confirmed the 4-pin pinouts above.)

    IMG_2503.jpg
    IMG_2500.JPG
    IMG_2501.jpg
    IMG_2502.jpg
    Last edited by LongTallTexan; 05-23-2023 at 11:00 AM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  8. #33
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    i was able to find the sensor from the part number on amazon and a bunch of other places.

    bosch f00c2g2040

    Amazon.com: X AUTOHAUX Car Mass Air Flow Sensor Meter Replacement F00C2G2040 for VW Jetta 1.8L 2000-2005 for Audi TT 1.8L 2001-2006 : Automotive


    most places don't list the number of pins but it shows up when searching specifically for a 4-pin maf. the other part number was for the housing only.

    go to a wrecker and pull one off a vw to check.

  9. #34
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    That one is a 5-pin.

    But in the "related Products" there was a 4-pin, and I ordered it! Thanks.

    https://www.amazon.com/dp/B07LBF9CQ9...WxfdGhlbWF0aWM
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  10. #35
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    So I called up the local BMW indy mechanic and they referred me to another with a bit more E30 tuner experience.

    Basically I told them about my situation - I think I have a bad MAF I cannot identify from Miller (out of business) Performance MAF/chip upgrade. The mechanic was nice and basically told me I was shit outta luck. Suggested I call Turner Performance for some advice.

    We both figured if I can't happen across the right MAF, might be best to go back to stock AFM with a new chip. Talked to Turner and they confirmed.

    But never to be persuaded, I soldier on.

    This is a similar MAF I am returning to Amazon (an Audi/VW application). You can see it's like my MAF connector shape. That is under my connector fitting! But the pins are deep in the new unit.
    IMG_2508.JPG

    I actually found a Bosch MAF sensor part, but it was not available. But it directed me to a generic MAF sensor with that Bosch part number. So I bought it.
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    And a pigtail too.

    I'll see what I can do with that this weekend.
    Last edited by LongTallTexan; 05-24-2023 at 10:33 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  11. #36
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    And for some more research, I measured my MAF signal at idle and got 2v. Everything I read says I should be about 0.9v at idle.

    And with the rich fumes it made sense that the signal was wrong from th e MAF - maybe defective.

    So, I wired up a 1v signal using a AA battery and a couple resistors.

    When I gave the ECU a 1v signal, the car started and idled great!

    Maybe the MAF is bad.

    Saga continues.
    IMG_2509.jpg
    IMG_2510.jpg
    IMG_2511.jpg
    Attached Images Attached Images
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  12. #37
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    Research continues. The generic MAF sensor that popped up with the Bosch element number references applications for both VW Jetta 1.8L 2000-2005 and Audi TT 1.8L 2001-2006.

    I looked up the 2001 Audi TT 1.8L Turbo (no others) on RockAuto and the Bosch MAF that popped up has the exact same part number on the housing!
    Screen Shot 2023-05-25 at 2.41.34 PM.png
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  13. #38
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    Nothing I've tried seems to work. The new MAF is just as bad as the old MAF.

    The 5V ref from the ECU is 5V with the engine off and ignition on. But with the engine running it is under 3V. I have no idea if that is good or bad.

    So, I bit the bullet and ordered an AFM from Rockauto and a new chip to replace the Miller Performance chip from Turner. If that doesn't work, I'll probably get a used ECU to see it that works.

    Fingers crossed.

    BTW, this is by the ECU, any idea what it is for?
    IMG_2512.jpg
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  14. #39
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    Quote Originally Posted by LongTallTexan View Post
    Threw another part at it, the cam sensor. And new cap, rotor and plugs while I was at it.

    Pulled the brain and checked on the chip. It is the Miller chip upgrade for MAF sensor. (I re-wrote the green writing in black.)

    I looked at the circuit board and everything looks good. Nothing burned or discolored. All soldering looks good.

    This now seems to the regular symptoms when driving a loop with lots of curves and hills.

    Drives GREAT!!!! For a few miles. Then on a fairly steep uphill grade running at 3k rpm, the engine starts losing power and "lunging."

    Over 4k rpm, with my foot in it, runs fine.

    I pull over, shut her down. Disconnect the MAF connector. Plug it back in.

    And it runs great again!

    Maybe the connection. Maybe the MAF is really going out.

    Any thoughts appreciated.
    Attachment 715712Attachment 715713




    Cap and rotor? Really, where are these mythical parts from yesteryear found on your car?

    When you turn the key to Position II (RUN), before START, does the Service Engine Soon light come on? If no, then you need to pull codes because it's not possible that the car can be running this poorly and not be throwing codes. The SES light is required to come on, if it does not then you either have a failed bulb or an ECU that does not work. The SES light should be on at any time that the key is set to RUN but the engine is off, the light goes out after engine start and then comes on again if there is a fault code.

    "MAYBE," is a poor way to diagnose problems on a motor vehicle. You have a car that's been chipped, the MAF has been changed or modified, whatever, and now the engine does not run. This should be a clue. You need to know what the chip is supposed to do, then figure out if it's doing it. You report, "nothing burned or discolored," with respect to the ECU, but this does not mean that the ECU is good. Lots of stuff can be wrong that has nothing to do with components having their own versions of Three Mile Island.

  15. #40
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    Quote Originally Posted by JDStrickland View Post
    Cap and rotor? Really, where are these mythical parts from yesteryear found on your car?
    Ummm on the front of the engine where you would expect to find a cap and rotor? Did you stumble into the e30 forum on accident? There is no SES light as you describe on an e30 and only the ones at the end of the model run had very limited codes that could be pulled.
    Last edited by sienayr; 05-31-2023 at 06:17 PM.

  16. #41
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    Quote Originally Posted by sienayr View Post
    Ummm on the front of the engine where you would expect to find a cap and rotor? Did you stumble into the e30 forum on accident? There is no SES light as you describe on an e30 and only the ones at the end of the model run had very limited codes that could be pulled.
    Thanks. I was getting paranoid the PO disconnected that too!

    Fuel filter is a couple years old, but have a one on the way for tomorrow.

    I really don't like to fly blind, but what the hell?
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  17. #42
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    Well, nothing seems to work involving the old or new MAF. It's gotten to where it is hard to just get the car down the drive and around the culdesac.

    So I bit the bullet and ordered an AFM to take it back to stock. (RockAuto has them.)

    Well that and a chip from Turner Motorsports to replace the Miller Performance chip.

    I now need to confirm the pin-outs to the AFM.

    Here is what the Motronic 1.3 diagram says is stock for the AFM:

    Added this below as a picture (so you can read it better)
    ECU pin / AFM pin / wire / Stock function / Miller
    44 / 1 / GY/VI / Air Temp / 5v ref
    7 / 2 / GY/YL / AFM input / MAF ref
    12 / 3 / GY/WH / Ref output / 12v
    26 / 4 / GY/BU / Ground / Ground
    Screen Shot 2023-06-05 at 2.22.31 PM.png

    So this scares the crap out of me.

    I presumed the Miller MAF upgrade was just the MAF sensor and a chip.

    But this seems like the pins are rewired. With the Miller chip, here are some measurement:
    pin 1 measures 5v with the ignition on. But while running it drops to 2.75-3v
    pin 2 measures 0.1v with ignition on, and jumps to 2v while running. And increases with rpm. (Rule of thumb, I read the MAF should put out just under 1v at idle.)
    pin 3 does the AMF even want 12v?

    Maybe I need a to get a used ECU to plug it in with the AFM.

    Does any of this make sense to anyone?
    Last edited by LongTallTexan; 06-05-2023 at 03:36 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  18. #43
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    Just for fun, I put it all back together with the original MAF.

    Cleaned the three relays on the driver's side fender.

    Started her up, and she ran like crap. Barely idled. Barely rev'd. But I kept her going and managed to get her to rev. Kept at it for 3 or 4 minutes in the driveway.

    Then she started idling great and revving great.

    So I took her for a drive around the neighborhood and she ran great.

    Then after about a mile on the way back, started running like crap again.

    What the....
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  19. #44
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    Quote Originally Posted by LongTallTexan View Post
    Just for fun, I put it all back together with the original MAF.

    Cleaned the three relays on the driver's side fender.

    Started her up, and she ran like crap. Barely idled. Barely rev'd. But I kept her going and managed to get her to rev. Kept at it for 3 or 4 minutes in the driveway.

    Then she started idling great and revving great.

    So I took her for a drive around the neighborhood and she ran great.

    Then after about a mile on the way back, started running like crap again.

    What the....
    what is your fuel pressure doing when this is happening ?

  20. #45
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    I don't have a fuel pressure gauge. Pump was replaced 2 years ago.

    I had fuel pressure gauges for my 928 with CIS. Don't know much about "modern" FI.
    Last edited by LongTallTexan; 06-05-2023 at 07:55 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  21. #46
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    Quote Originally Posted by LongTallTexan View Post
    I don't have a fuel pressure gauge. Pump was replaced 2 years ago.

    I had fuel pressure gauges for my 928 with CIS. Don't know much about "modern" FI.
    tee a gauge in under the hood. there's piles of diys on it. check both running and resting pressure to see how much it loses. see what it is doing when the car is not running correct.

  22. #47
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    Hallelujah!!!! This thread gets to go dormant!!!

    I took the advice to take her back "stock." That means a Turner Performance Chip to replace the Miller MAF upgrade chip, revert the wiring harness to stock, and replace the MAF with (can you believe it) a $90 rebuilt AFM from RockAuto!!!!

    I got the hiring harness fixed yesterday, and today, I got the AFM in.

    I connected the ground to the battery, held my breath, and IT STARTED RIGHT UP!!!!!

    Idle is good.

    I could hardly contain myself.

    I took her for a spin for a few miles on hilly and winding roads, and she ran GREAT!!!!

    I think that Turner chip is very refined. And maybe the AFM is just engineered better than a MAF upgrade.

    With the Miller upgrade, I had flat spots and really inconsistent throttle response. I don't want to dis the chip, but could it have been the problem - maybe with a MAF going south.

    I am so happy right now!!!

    IMG_2518.jpgIMG_2524.jpg
    Last edited by LongTallTexan; 06-08-2023 at 08:09 PM.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  23. #48
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    good fix.

  24. #49
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    Quote Originally Posted by 82eye View Post
    good fix.
    And thank you for your advice and encouragement!

    I bought a fuel pressure kit, but did not use it yet.

    I don't know why I was so apprehensive to test the fuel pressure, I slept with my fuel pressure gauges when I had my '78 928 with CIS.
    Dan Perez | 2002 E39 530i | caretaker 1989 E30 325i 4 door

  25. #50
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    Just an FYI - I ordered one of these AFM's also - I don't need one now, however the only place I knew to get one refurbed was bavarian restorations - https://bavrest.com/index.html

    Although I hear great things about his refurbed AFM - the price is $500 + https://bavrest.com/pricing.html

    Appreciate you letting us know that RA has them (or more precisely - Blue Streak Electronics)
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