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Thread: What does the MAF do?

  1. 06-27-2005, 03:52 PM #1
    stu1
    stu1 is offline Big Time Poster
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    Default What does the MAF do?

    I know it's supposed to tell the DME how much air is going through; but today I disconnected mine (so I'd know how it felt if it broke) then went for a drive and I really couldn't tell any difference at all?!?

    Is this normal? If you disconnect the MAF does it just drive like it normally does?

    Confused,
    Stu.
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  2. 06-27-2005, 03:54 PM #2
    bahnstormer
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    Default

    the maf is used to
    make
    apple
    flapjacks
    =]

    sorry can't help ya =]
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  3. 06-27-2005, 05:09 PM #3
    George Davis
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    Modern electronic engine management systems have some redundancy built in, so they can run ok with a bad sensor or two. MAFs measure air flow directly, but with other inputs the brain can figure out air flow close enough to do the job. RPMs and manifold absolute pressure and/or throttle position can be used to estimate air flow, and the O2 sensor is used to trim it. Plus it's probably stored a look-up table it can use if it's missing an input. At least that's how it worked in a 1996 Mustang I had.
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  4. 06-27-2005, 08:23 PM #4
    Javier
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    Default At least, did you get the check engine light??

    Javier
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  5. 06-28-2005, 05:21 PM #5
    JAlfredPrufrock
    JAlfredPrufrock is offline Big, Big Time Poster
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    Mass Airflow Sensor... if I were you I'd probably disconnect the negative terminal on the battery for an hour or two today and then reconnect the MAF to avoid any issues that may arise.
    1990 BMW 535i 5 speed - Black on Grey, LSD
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  6. 06-28-2005, 05:27 PM #6
    stu1
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    No, no CEL. I guess what I was asking is does anybody else with an M50 notice any difference with the MAF disconnected?
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  7. 06-28-2005, 05:56 PM #7
    Javier
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    Default Guess that as George told to us, your car has ...

    learned about the air density in the area you normally drive, and is using that memory to handle air mass parameters. You will probably notice something going wrong taking the car to another area (High mountain roads for example), were the air density will differ.

    Wonder why aren't you getting a CEL warning (guess you have one, I don't). Have never tried to unplug my equivalent device though.

    Javier
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  8. 06-28-2005, 06:33 PM #8
    stu1
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    So, if I unplug the MAF and then disconnect the battery for an hour...

    As for the CEL, I've never seen it light in my car (and I would have thought it should have lit when the MAF is disconnected) - maybe it isn't fitted; I've never had the instrument cluster apart to find out. It not being fitted would explain why I've never had any luck getting a stomp test going.

    Oh well.
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  9. 06-28-2005, 07:07 PM #9
    Dan in NZ
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    Could be that the CEL bulb is burnt out... Shouldn't it come on briefly every time you start the car? I wouldn't know, I don't have a CEL.
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  10. 06-28-2005, 07:17 PM #10
    Javier
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    Default Just like me, may be stu1 is also european.

    Javier
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