Tweecer RPM output all over the place

Discussion in '1994 - 1995 Specific Tech' started by 94-302-vert, Apr 28, 2010.


  1. 94-302-vert

    94-302-vert Active Member

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    My bud's 94 GT, AODE to 5speed conversion, when he datalogs the RPM is not consistent. Even to the point that on a full throttle acceleration run the rpms will go 4100 4120 4150 4100 4200 etc... all over the place...

    Any thoughts?
  2. BlackVert

    BlackVert Mustang Master

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    i'll look at mine, but that is probably sorta normal. i know that at idle, mine can be anywhere +/- 100 of what the gauge shows. there is some hysteresis built into the gauge
  3. RatStang

    RatStang New Member

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    When I had my TwEECer R/T, it was the same kind of crap. I ended up making a cheapo inductive pickup and wrapping it around the +1 plugwire insulation and it worked great. (Until I sold that POS to save myself the aggrevation. lol)
  4. 94-302-vert

    94-302-vert Active Member

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    I don't buy that it is normal... we did some back to back datalogs in the driveway the other day. Used a mechanical stop to open the throttle... at a stady throttle m car sould vary by +/- 30 RPM, his +/- 100 RPM. By 2k rpm my was VERY consistent and his was even more wacky...
  5. BlackVert

    BlackVert Mustang Master

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    well, my understanding is that that signal comes from the distributor, so maybe his dizzy is getting old?

    or my understanding is incorrect ...

    how does it run?
  6. toyman

    toyman SN Certified Technician

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    I suspect the PCM takes a signal from the PIP (pin 56) for rpm values. When I installed the Zeitronix WB controller tapping into pin 56 was the only way to achieve a steady rpm signal to the controller.
  7. 94-302-vert

    94-302-vert Active Member

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    Blackvert: His dizzzy is in prtty good shape. He has actually rebuilt it with a new PIP and that did not make things better.

    Now we also did the hold RPM test with and without the spout in place and the curve looks essentially the same.

    Toyman, did you tap into pin 56 at the computer or under the hood?
  8. toyman

    toyman SN Certified Technician

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    At the computer. It was easier as I had to cut the NB O2 wires (pins 43 & 42) and tap into 43 for the WB. Additionally, I ran a dedicated ground from the battery to the ECU chassis ground for the WB as well. Just made sense to do everything in one location.

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