How much play in the Dizzy? Causes of Knock?

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  • newsh
    S2Forum Obsessed
    • Aug 2003
    • 16226
    • Country: United Kingdom

    #1

    How much play in the Dizzy? Causes of Knock?

    What do you chaps think of this?

    Click this for a video vvv



    I'm using the hall sensor in the dizzy for the ABY ECU so no sparks in there, there's not much lateral play I can detect but it moves up and down a lot. There's also a little oil getting in, I can see it through the trigger window.
    I'm wondering if this could be the cause of my strange knocking symptoms. I remember years ago having problems with the car when Mihnea was mapping it, every now and then it would throw a big misfire and a cloud of smoke out the back. Mihnea said he thought the dizzy might not be lined up right, the ECU would see the hall trigger go out of the window and react as though it was knocking and throw a load of fuel in to put out the fire. I had a look and sure enough the marks were off by a few mm at TDC. Corrected it and the car has run great for about another 100,000 miles. Till now when it seems to be recording knock (but I'm not hearing it knock) And it's done a few big cutouts at full and sometime part throttle and sometimes the ECU resets.

    BTW I just checked the timing marks and they look pretty good, a bit dark and cold to really be 100% sure at the mo.

    What other possible causes of knock are there, it seems to mostly be happening on cylinder 4 but the other cyliders are showing some too.

    Compression is a healthy 10.5 - 11 Bar on all 5.

    Last edited by newsh; 2 March 2015, 22:36.

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  • A1QSHIP
    S2Forum Maniac
    • Aug 2004
    • 975
    • Country: United States

    #2
    On my first 7a powered Coupe I had a inner exhaust valve spring that broke. The knock sensor interpreted this as spark knock & pulled timing. It sounded like a distributor gear rattling about.
    HTH, Chris
    "Nulla tenaci invia est via"

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    • 220bhp
      S2Forum Fiend
      • Nov 2004
      • 2578
      • Home: United Kingdom

      #3
      John I changed my distributor because it had play, just like yours. But afterwards I was told that under rotation It is forced into one position. I have a distributor of the doner car I bought, If I can find it. I will see if it is the same. How many miles have you done since your rebuild.

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      • prj
        S2Forum Zealot
        • Mar 2010
        • 6308
        • Country: Estonia

        #4
        Distributor misalignment won't make the ECU see knock.
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        • mike74
          S2Forum Maniac
          • Apr 2014
          • 615
          • Country: Scotland

          #5
          Probably more of a fuelling problem I'd think. Has the FPR ever been replaced?

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          • SteveH
            Super Moderator
            • Jul 2003
            • 4460
            • Country: United Kingdom

            #6
            I have the head off my motor John so I can check to see what movement I have in the dizzy. I'm replacing the head with an ABY head so need to graft the hall sensor wires from the ABY unit into the old 3B wiring which is connected to an ABY ECU. I recon I could hear some rattling from the top of the head on my car which sounded like it was the dizzy or dizzy drive gear. I was most noticeable when blipping the throttle from idle.
            91 Modded 3B
            14 A6 Avant Black Edition

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            • UrS4boy
              S2Forum Obsessed
              • Feb 2006
              • 11859
              • Country: Canada

              #7
              Originally posted by SteveH
              I'm replacing the head with an ABY head so need to graft the hall sensor wires from the ABY unit into the old 3B wiring which is connected to an ABY ECU.
              You could just extend the wiring using one or both of the 21/22 three pin connector pair (or not):

              RS2'd 93 UrS4 5 spd sedan
              94 UrS4 V8 6 spd manual avant

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              • sidrick
                S2Forum Extremist
                • Jan 2011
                • 1342
                • Country: Scotland

                #8
                Cut your nails

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                • SteveH
                  Super Moderator
                  • Jul 2003
                  • 4460
                  • Country: United Kingdom

                  #9
                  Originally posted by UrS4boy
                  You could just extend the wiring using one or both of the 21/22 three pin connector pair (or not):

                  Cheers

                  Connectors won't be the problem, it will be getting the wires joined up correctly
                  91 Modded 3B
                  14 A6 Avant Black Edition

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                  • newsh
                    S2Forum Obsessed
                    • Aug 2003
                    • 16226
                    • Country: United Kingdom

                    #10
                    Originally posted by mike74
                    Probably more of a fuelling problem I'd think. Has the FPR ever been replaced?
                    FPR and injectors are brand new, 044 pump and filter are not that old, wideband says mixture is good.

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                    • newsh
                      S2Forum Obsessed
                      • Aug 2003
                      • 16226
                      • Country: United Kingdom

                      #11
                      Originally posted by prj
                      Distributor misalignment won't make the ECU see knock.
                      Ok, well that's what I was told when we mapped the 3B ECU and it certainly fixed the problem, so maybe it's just the ECU resetting.

                      Is it possible this is a mechanical knock, like a small end or a bad lifter or is it definitely pinging. Because I know what pinging sounds like and I don't think it is.

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                      • newsh
                        S2Forum Obsessed
                        • Aug 2003
                        • 16226
                        • Country: United Kingdom

                        #12
                        Originally posted by A1QSHIP
                        On my first 7a powered Coupe I had a inner exhaust valve spring that broke. The knock sensor interpreted this as spark knock & pulled timing. It sounded like a distributor gear rattling about.
                        HTH, Chris
                        Interesting, there is a weird rattle that comes and goes, not very loud but sometimes there when blipping, I'm tending towards a mechanical problem rather than detonation.

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                        • newsh
                          S2Forum Obsessed
                          • Aug 2003
                          • 16226
                          • Country: United Kingdom

                          #13
                          Originally posted by sidrick
                          Cut your nails


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                          • newsh
                            S2Forum Obsessed
                            • Aug 2003
                            • 16226
                            • Country: United Kingdom

                            #14
                            Originally posted by prj
                            Distributor misalignment won't make the ECU see knock.
                            On one of the logs, the RPM max was 10,400 RPM. Does that suggest anything? (probably double what the actual log should have been.)

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                            • newsh
                              S2Forum Obsessed
                              • Aug 2003
                              • 16226
                              • Country: United Kingdom

                              #15
                              I was going to look at the flywheel sensors and make sure they're clean but the bolts are nasty so it will have to wait..

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