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S52 Coil Testing

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    #1

    S52 Coil Testing

    My boosted S52 started misfiring under boost badly within the past week. Replaced plugs with the same plugs and the same gap and that did not help the issue. I tested all of the coil packs and they were within 1-1.1 Ohms each which should be in spec with a baseline of .3 from my multimeter.
    Is there another test for coilpacks besides resistance between the two outer pins?

    This issue just started last week and has been getting worse, with the plugs out of the question I'm pretty sure it has to be a coil going but I just don't want to buy 6 to replace it with.
    Thanks,
    Matt

    Check out my BMW Fault Code Index
    '89 Turbo M20 Zinno Cabrio (scrapped)
    '89 Zinno IX (sold)
    '91 Granit Turbo S52 Sedan (scrapped)
    '91 WIP (scrapped)
    '13 F10 Carbon Black 550iX MSport
    '91 iX Sedan
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    #2
    Is the misfire present at idle? If so, you can disconnect the coils one by one while the motor is running. When you disconnect the one that does not change the way the motor is running, you've found your bad coil.
    After that you could check fuel pressure, after that it would be things like injectors and compression.

    Comment

      #3
      You can also load test the coils in a somewhat similar manner. Pull the coils up off the plugs one by one while the engine is running and see how high you can get each one before a misfire develops. Youll obviously hear a popping as teh coil is jumping the gap to the plug. A weak coil will typically not be able to jump any sort of gap.

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      Comment

        #4
        Sometimes the coil drivers don't like to be plugged and unplugged while running, I was always instructed not to use the pull/listen method with non distributor ignition systems...megasquirt or not. Junkie would know best though. No difference between the old plugs? Is one dirtier than the others?

        If you have an in fared thermometer, check individual exhaust port temps and compare. If u find a cold port, swap coils and see if the cold port changes with the coil

        Comment

          #5
          No misfiring at idle or low loads, only loads above 100%. And after some more driving I found out it only happens when I've been driving for a while. Also, if I go into boost hard and fast it usually misfires a couple of times but if I stay at a high RPM for a while then ease into boost it's a constant smooth misfire like it's running on 5. This leads me to believe one is failing when it gets hot.

          The old plugs all looked pretty similar, I was surprised. But right as the misfire started happening I got on changing the plugs and I avoided boost beforehand so they weren't exposed to many misfires.

          Thanks for the suggestions though, I'm going to switch them out one at a time with a known good one. If that doesn't work I'll try the jumping the gap method to see if I can narrow it down to any specific coils.

          Merry Christmas!
          Thanks,
          Matt

          Check out my BMW Fault Code Index
          '89 Turbo M20 Zinno Cabrio (scrapped)
          '89 Zinno IX (sold)
          '91 Granit Turbo S52 Sedan (scrapped)
          '91 WIP (scrapped)
          '13 F10 Carbon Black 550iX MSport
          '91 iX Sedan

          Comment

            #6
            Brand new injectors and fuel filter? What fuel pump are you running?

            Comment

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