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Missing / Flatspot / Missfire after 4,000rpm ​​​​​​​

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  • Missing / Flatspot / Missfire after 4,000rpm ​​​​​​​

    Missing / Flatspot / Missfire after 4,000rpm

    If I was a betting man, if it is a coil That is causing my issue, then it’s going to be number 2 Coil as my #2 Spark plug is the blackest !

  • #2
    more info on your setup ?

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    • #3
      ....
      Last edited by UUUdirs2newcastle; 15th July 2020, 01:01.

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      • #4


        The car was fine when I parked her up in the garage 8 years ago!

        Kim Collins upgraded the car back in 1998 to a MTM 380hp K24/K26 Hybrid Turbo

        Good Points

        Brand New Bosch 040 Fuel Pump

        Brand New Bosch 787 Fuel Filter

        Audi V8 Large Fuel Pump Basket

        Brand New NGK PFR7B plugs (gapped to 0.6mm

        Full Tank of Super Unleaded

        Brand New Samco Induction Silicone Hoses

        Bad Points

        Original 20 year old Audi / Beru Coil Packs x 5.

        Original 3.5mm Vacuum Hoses throughout the engine bay. (Maybe I should replace them all)

        Im using the original Bosch 3.8 FPR (This has a dent/squash in the top, is that on purpose to get more pressure?)

        The very short silicone hose between Intercooler & front crossmember pipe is there, and it’s old, I have not changed that yet.

        I have not pressure tested the induction for boost leaks or any of the small 3.5mm vacuum tubes through the engine bay.

        I have not pressure tested the fuel delivery.

        The Coil Pack rubber spark plug tubes are the original ones, maybe I should replace those too?





        Last edited by UUUdirs2newcastle; 15th July 2020, 01:00.

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        • #5
          ...
          Last edited by UUUdirs2newcastle; 15th July 2020, 01:02.

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          • #6
            Very easy to test this usually. Try give it half throttle instead of WOT through the gears. Most likely your coils are due a change.
            1996 S2 ABY Silver

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            • #7
              Originally posted by rynaqui View Post
              Very easy to test this usually. Try give it half throttle instead of WOT through the gears. Most likely your coils are due a change.
              Driving through the gears it drives great, up to 3,500 / 3,800 rpm, but more than half throttle, when it goes to 4,000 rpm, it’s just flat as anything, I was wondering if I had a vacuum leak or a turbo pipe leak as there was a feeling of no boost, but I think after what all you guys are saying, it’s the Coil that’s the issue.

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              • #8
                maybe it could be your coils, i where also thinking bad crank sensor, is it 4000rpm i all gears ?

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                • #9
                  Do a modern tsfi coil conversion. Best thing I ever did to my ABY. Driving it after conversion felt like it had a lighter flywheel fitted, weird explanation but great to drive.

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                  • #10
                    Originally posted by mllen89 View Post
                    maybe it could be your coils, i where also thinking bad crank sensor, is it 4000rpm i all gears ?
                    I’m not sure, the rpm varies depending on throttle and gear if I recall correctly.

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                    • #11
                      ok :S do you have knock sensors? its a aby right ?

                      Comment


                      • #12
                        from your other thread


                        Originally posted by UUUdirs2newcastle View Post
                        Would a leak from one of the little 3.5mm vacuum hoses that are all over the engine cause this if there was one perished? They all seem a little iffy. Probably 26 years old !


                        Yes, these little tubes are responsible for applying vacuum or boost pressure to the ECU to calculate fuel and timing and the Fuel Pressure Regulator to adjust fuel pressure.
                        If these tubes are not completely sealed and in perfect condition the car will not run right.

                        You must do proper boost leak test!

                        S2 Coupe 3B Project


                        Ur quattro restoration

                        S2 Avant

                        Boost is the new rock and roll!
                        sigpic

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                        • #13
                          You won’t believe it ! I’ve found the boost leak! The rubber O - Ring on the MTM solid intake pipe had broken causing a air leak. I’m trying to source a new O-Ring now.

                          It least I only bought ‘ONE’ new Beru Coil. ! ha ha ha
                          Attached Files

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                          • #14
                            Well done!
                            There will probably be more leaks though

                            Now buy some vac tube and replace all the lines, either with Audi stuff with the braided cotton outer or good quality silicone stuff, with new clips.

                            S2 Coupe 3B Project


                            Ur quattro restoration

                            S2 Avant

                            Boost is the new rock and roll!
                            sigpic

                            Comment


                            • #15
                              Oh man, these rubber o rings are hard to get, I’ve got 2mm, 2.5mm, 3.5mm and all wrong :-(

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