Missfire until hot

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  • smogthemog
    S2Forum Enthusiast
    • Oct 2006
    • 149
    • Home: United Kingdom Current: England

    #1

    Missfire until hot

    My urS6 has a horrible missfire until it reaches temperature. It sounds like its running on 4 sometimes 3 cylinders. I've changed coil packs to the 1.8t conversion, new plugs and it still does it. The vehicle is sorn at the moment and hasn't been run properly on the road for 2.5 yrs, only started and ticked over till hot.
    When it was taken off the road it had this missfire but then i couldn't afford to sort it. Now I can and intend in doing so but its baffling me.
    When I first start it from cold, for the first 30 seconds it runs fine but only if I don't touch the pedal. If I do touch the pedal it runs like a bag of *****! Nearly cutting out. It does this until its hot then it ticks over alot better but still coughs a bit when accelerated. After it dies down it then missfires for a few seconds then its ok.
    As I said, I replaced the coil packs and have tried new plugs but its still the same.
    When its ticking over and missfiring I can disconnect each fuel injector and I can hear each one make a difference to engine note so I don't 'think' its injector based.
    Any help appreciated
    Jim B
    97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

    http://smogthemog.blogspot.com/
  • newsh
    S2Forum Obsessed
    • Aug 2003
    • 16226
    • Country: United Kingdom

    #2
    Have you done a boost leak test?

    Is your ISV working properly?

    Have you tried cleaning the MAF connector? (just unplug the MAF, plug it in and out a few times, give it a good wiggle, plug it back in, start the car and see if it's different.)

    S2 Coupe 3B Project


    Ur quattro restoration

    S2 Avant

    Boost is the new rock and roll!
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    • smogthemog
      S2Forum Enthusiast
      • Oct 2006
      • 149
      • Home: United Kingdom Current: England

      #3
      ISV?

      I don't think its a boost leak as I went through all that before I sorn it. I did lots of checks and couldn't find any leaks.
      This is more of an obvious missfire than a boost leak. I may video it when I get a mo.
      I also think my turbo is ******ed as when its cold it makes strange squeeling noises if you rev it a bit. Been dodgy for a while hence my other thread asking for a Turbo upgrade
      Jim B
      97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

      http://smogthemog.blogspot.com/

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

        #4
        Idle Stabilisation Valve, it's at the back of the inlet manifold, controls the idle speed, they can get gunked up. Take it off, wash it out with WD40 and see if that helps.

        S2 Coupe 3B Project


        Ur quattro restoration

        S2 Avant

        Boost is the new rock and roll!
        sigpic

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        • smogthemog
          S2Forum Enthusiast
          • Oct 2006
          • 149
          • Home: United Kingdom Current: England

          #5
          I'll try it. Thanks
          Jim B
          97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

          http://smogthemog.blogspot.com/

          Comment

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

            #6
            Do you have Vagcom to read the codes?

            S2 Coupe 3B Project


            Ur quattro restoration

            S2 Avant

            Boost is the new rock and roll!
            sigpic

            Comment

            • smogthemog
              S2Forum Enthusiast
              • Oct 2006
              • 149
              • Home: United Kingdom Current: England

              #7
              No but I do have a code reader/eraser. I'll try that too.
              Jim B
              97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

              http://smogthemog.blogspot.com/

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

                #8
                Cool, wondering if the white coloured temp sensor on the back of the head is not working or shorted wiring in the connector rubber boot.

                S2 Coupe 3B Project


                Ur quattro restoration

                S2 Avant

                Boost is the new rock and roll!
                sigpic

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                • andyg plym
                  S2Forum Freak
                  • Nov 2006
                  • 4646
                  • Country: England

                  #9
                  I'm going to hedge my bets on the maf, just going on my recent experience.
                  I had no maf fault code either.
                  Mine would miss badly, you couldn't Rev it until warm, then all of a sudden after 5 minutes it was like a light switch-the engine note would change and away I'd go

                  Comment

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

                    #10
                    AAN Engine Bay Device Map (live link version)

                    Originally posted by smogthemog
                    ISV?
                    Click on the N71 ISV and the G70 MAF labels on this UrS Engine Bay Device Map to learn more about cleaning both.



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

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                    • PRY4SNO
                      S2Forum Maniac
                      • Mar 2009
                      • 767
                      • Country: Canada

                      #11
                      Originally posted by newsh
                      Cool, wondering if the white coloured temp sensor on the back of the head is not working or shorted wiring in the connector rubber boot.
                      This.

                      Had a similar issue.

                      Turned out to be the POS and/or coils were shot. When I got a harness from Norbitron and some TFSI coils, problem was solved.
                      2013 Touareg TDI /// #farmenwagen
                      1992 80q 20v /// Eventual AAN'd Winter Sled
                      1990 Cq /// Project: Because Racecar

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

                        #12
                        Originally posted by PRY4SNO
                        This. Had a similar issue. Turned out to be the POS and/or coils were shot. When I got a harness from Norbitron and some TFSI coils, problem was solved.
                        I would agree with you but, he says:

                        Originally posted by smogthemog
                        My urS6 has a horrible missfire until it reaches temperature. It sounds like its running on 4 sometimes 3 cylinders. I've changed coil packs to the 1.8t conversion, new plugs and it still does it.
                        RS2'd 93 UrS4 5 spd sedan
                        94 UrS4 V8 6 spd manual avant

                        Comment

                        • PRY4SNO
                          S2Forum Maniac
                          • Mar 2009
                          • 767
                          • Country: Canada

                          #13
                          Right. Forgot to say that I'd first tried changing the white coolant temp sensor at the back of the head.
                          2013 Touareg TDI /// #farmenwagen
                          1992 80q 20v /// Eventual AAN'd Winter Sled
                          1990 Cq /// Project: Because Racecar

                          Comment

                          • smogthemog
                            S2Forum Enthusiast
                            • Oct 2006
                            • 149
                            • Home: United Kingdom Current: England

                            #14
                            I'll try that first.
                            Jim B
                            97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

                            http://smogthemog.blogspot.com/

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                            • smogthemog
                              S2Forum Enthusiast
                              • Oct 2006
                              • 149
                              • Home: United Kingdom Current: England

                              #15
                              Does anyone have the name or numbers of this temperature sender so I can get one ordered please?
                              Thanks
                              Jim B
                              97 S6 AAN Quattro Avant C4 | Powerflow Cat Back EX | Milltek Hyperboost RV | MAC N75 Valve | FMIC | HID's (Dip & Fog's)| MRC Re-map SII | Carbon interior | De-chromed | Short shift | Samco Air Hoses |

                              http://smogthemog.blogspot.com/

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