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Weird rough idle

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  • #16
    Figured it out. At first my VAF was angled up (inlet higher than outlet). I did not have the IAC hooked up at this time. I remade my pre-turbo piping too let the VAF sit parallel to the ground, and tapped in my IAC. This is when I started to have the odd idle issue.

    Fastforward through all the troubleshooting I've done recently and lastly I noticed that the VAF is very sensative to angle adjustments at idle. Also noticed, that if I barely touched the VAF flapper that the car would clear up and idle perfectand stop running rich. I wondered if being turbo had any ill effects to amount of flapper angle/air volume/pressure within the preturbo pipe as apposed to being N/A.
    So I rotated the VAF within the coupler to see if gravity would adjust the Flapper to compensate for any of these theoretical problems. I rotated the VAF 90* degrees (counter clockwise if looking into the intake of the VAF (tried all other angles too) but found this angle to be where the VAF is happiest. Which happened to be with the pigtail connector at the top . and now the car purrs like a kitten at idle, and drives better too! No surging, no extremely rich smell or burning of the eyes lol.

    Anyone else ever encountered a VAF angle problem?
    '93 BP-T 57trim TO4E - Coilovers - 13x7 steelies - 175/60 - 48k mi

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    • #17
      Glad to hear you got it figured out
      1992 white L, Bp, American racing 13's, stock trans.
      1991 White L, BP/F5MR, protege header, full aspire swap with gr2's, seats, and sway bar, 15" konig's, short throw, escort console.
      1991 blue L, 5 speed.
      1988 red L-plus-all stock.

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      • #18
        Awesome ! Have had to adjust a few VAF but never because of angle. Some wouldn't
        adjust because of a bent door .
        Reflex paint by Langeman...Lifted...Tow Rig

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        • #19
          That is very interesting. My BP Festiva has the exact same problem. I will take a look at the VAF and see if that is it.

          -1989 festiva auto to standard conversion, bp g5mr white, aspire swap- October 2010 Festiva of the Month
          -1993 festiva stock standard blue, kia rio front struts

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          • #20
            My first guess was sticky VAF door, but yes... The VAFs are sensitive to angle because gravity will defy or help the door open and close too much. Stock, they sit level and the door rotates on an axis perpendicular to the ground. Gravity won't change spring rate and perceived air flow by the vane.
            -Zack
            Blue '93 GL Auto: White 13" 5 Point Wheels, Full LED Conversion, and an 8" Sub

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            • #21
              Man, all the time. SVOs are VAM cars, and they are VERY finicky when the VAM is moved around. I kept mine draw-thru to avoid some of the issues.

              Is yours a blow thru or draw thru VAM setup?
              1989 Carby L: Stock. Slow.
              1998 Mustang Cobra: ported heads, cams, longtubes, 4.30 gears
              2016 Focus ST: daily driven go-kart

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