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Boost Problem after long stop

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  • Boost Problem after long stop

    I have a strange boost problem in my S2, it was stopped in a hot garage around 2 months (temp. in a sunny day will be 50ºC or even more...)

    I drove it two days ago and the car goes fine as usually, but the max. boost what I have it's only 0,4bar. The last time who I drove it was perfect....after the stop no.

    I checked/changed n75 ( even a output test ), wastegate, turbo ( looks nice turbine/compressor wheel), FPR, Rs4 MAF, intake hose pressure test, MAP vacuum line, DV.

    I fitted a stronger wastegate spring, the boost was 1,2bar (mine is 1,7bar) and the turbo spins good and sound nice.

    I open the ecu to check the MAP ( stucked with a pice of rubber or something ) and was ok. I made again the intake hose pressure and check the MAP voltaje signal, I think that it's ok, These was the numbers (aren't totally accurate because to check the pressure I used the car boost gauge and it's mechanical):

    0bar--1,2v
    0,3bar--1,6v
    0,5bar--1,8v
    0,7bar--2,1v
    0,9bar--2,3v
    1,1bar--2,5v
    1,3bar--2,8v
    1,5bar--3v

    I think it's a motorolla 350 or 400kpa, was done by Dmitri

    Also I found rubber into the plastic catch tank MAP, but the line it's good

    https://i.pinimg.com/originals/3f/db...8deff19752.jpg

    The symptoms it's like the ecu forgot that he need to talk with the n75 to give me boost...it's a turbo engine not N/A

    Also when the rpms are high, and the boost will be 1,7bar not 0,4bar (spring rated), the AFR it's rich...lower 11

    And I can't test with other ecu because mine it's mod to use Rs4 MAF

    Ideas??????

  • #2
    If the boost signal (in the hard green plastic tubing) does not get to the MAP sensor, then the ECU does not react to intake manifold pressures and control the N75 WGFV accordingly. All you get is the WG spring pressure boost (about 0.4 Bar). This sounds like your issue.

    Have a read on this:

    http://forums.quattroworld.com/s4s6/msgs/20401.phtml

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

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    • #3
      Disconnect MFTS and try

      S2 Coupe 3B Project


      Ur quattro restoration

      S2 Avant

      Boost is the new rock and roll!
      sigpic

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      • #4
        Originally posted by UrS4boy View Post
        If the boost signal (in the hard green plastic tubing) does not get to the MAP sensor, then the ECU does not react to intake manifold pressures and control the N75 WGFV accordingly. All you get is the WG spring pressure boost (about 0.4 Bar). This sounds like your issue.

        Have a read on this:

        http://forums.quattroworld.com/s4s6/msgs/20401.phtml

        Hi mate! I tested the line and was ok, no leaks or stucked ...also I fit a straight vacuum hose from IM to the ecu and nothing changed...

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        • #5
          Originally posted by newsh View Post
          Disconnect MFTS and try
          yes! I forgot that the MFTS can cut the boost if the engine it's overheated or "think" that it's overheated due a false signal ( conector/wires problems or a faulty sensor)...I'll check it on monday

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          • #6
            I disconnected the 2R pin, I put independent connectors in the past, and nothing changes...also 4C for autocheck and nothing.

            The turbo eprom could be damaged??

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