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How much info can I get from a BMW engine diagnostic?

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    #1

    How much info can I get from a BMW engine diagnostic?

    My car has been having some issues:

    http://www.e30tech.com/forum/viewtopic.php?t=15984


    Summary:

    On a cold engine (even slightly cold) it runs very rough. Once up to temperature, it's great with no problems.
    I've found that disconnecting the battery (resetting the ecu) will fix my problem for about a day, and then it comes back again.

    I've come to the point where I need some professional help. I was thinking of taking it to an independant bmw shop (they know their shit...) and get them to hook it up to their diagnostic computer. My question is, are these things sophisticated enough to actually determine my problem? Or will it just tell me my fault codes (which I can read myself)?

    I'm hoping that their machine will be able to dive deep into my ecu and find my problems.... Am I chasing a dream?

    If anyone knows, I'd greatly appreciate some input before I spend a few hundred bucks on this.

    Thanks.
    Tags: None
    #2
    On an E30 all it can do is read fault codes, and display current sensor readings. Even then it can only read below 2000rpm, above that the processor in the Motronic isn't powerful enough to provide diagnostic outputs and run the motor. If you have a sensor that is way out of range you'll be able to see it on there; but it can't really do any diagnostic or functional testing like newer cars can.
    Adam Fogg- '88 M3

    Common sense- It's the new 'gifted'

    Comment

      #3
      Originally posted by AdamF 88iS
      On an E30 all it can do is read fault codes, and display current sensor readings. Even then it can only read below 2000rpm, above that the processor in the Motronic isn't powerful enough to provide diagnostic outputs and run the motor. If you have a sensor that is way out of range you'll be able to see it on there; but it can't really do any diagnostic or functional testing like newer cars can.
      Damn.... that's what I was fearing...

      Maybe I'll get it in for an hour and see if there's anything obvious. $80 wont kill me.

      Thanks.

      Comment

        #4
        Originally posted by ryan_george
        Damn.... that's what I was fearing...

        Maybe I'll get it in for an hour and see if there's anything obvious. $80 wont kill me.

        Thanks.
        i had the same problem, I looked for the problem for a long time, did lots of unnecisary things... took it to bmw specialists, independat mechanics, dealership (which i will never ever do again) and noone could figure it out. wasn't throwing any fault codes... so i figured what the hell, iv checked anything, ill buy another afm, and bam, fixed the problem. i tried everything including rebuilding, and resurfacing the head, rewiring, chip swapping, etc...
        my symptoms were:
        every time it started it would run a little rough for a couple min, a bit of throttle fixed the problem, but if i let it idle for like 5 min it would come back. If i drove it, the problem would disapear until i started it. If i disconnected the battery it would stop the problem for a day or 2. hmm, thats all i can remember for now...

        good luck!

        Comment

          #5
          Originally posted by kowalski
          i had the same problem, I looked for the problem for a long time, did lots of unnecisary things... took it to bmw specialists, independat mechanics, dealership (which i will never ever do again) and noone could figure it out. wasn't throwing any fault codes... so i figured what the hell, iv checked anything, ill buy another afm, and bam, fixed the problem. i tried everything including rebuilding, and resurfacing the head, rewiring, chip swapping, etc...
          my symptoms were:
          every time it started it would run a little rough for a couple min, a bit of throttle fixed the problem, but if i let it idle for like 5 min it would come back. If i drove it, the problem would disapear until i started it. If i disconnected the battery it would stop the problem for a day or 2. hmm, thats all i can remember for now...

          good luck!
          Thanks for that info.

          I went to the dealership today and asked the service consultant about my troubles. As soon as I said "e30" I saw a look of confusion in his face :loco:

          I didn't get much info from him, but I don't think he really knew what he was talking about. He has the impression that e30s came with hot-wire MAFs from the factory....:drink:

          Comment

            #6
            Check AFM and the ICV. I would try changing the AFM, and cleaning the ICV with some carb cleaner or whatever, or susbstitute it with a known working unit.

            Kyle
            1988 M3, 97 840, 99 XJ
            DILLIGAF

            Comment

              #7
              Originally posted by bimmer8604
              Check AFM and the ICV. I would try changing the AFM, and cleaning the ICV with some carb cleaner or whatever, or susbstitute it with a known working unit.

              Kyle
              I've tested the ICV and it's fine. Everything also works flawlessly once the ecu is reset.

              I've got an s50 MAF, not a stock AFM.

              Comment

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