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Hard Start, questionable TPS

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  • Hard Start, questionable TPS

    My 96 failed to start the other day (fortunately at home in the garage). No issues previous, but suddenly would not fire. Repeated start attempts would get one or two ignition pops then would die. Let it sit a couple days until I had time to get to it.

    Checked Fuel pressure and spark. Was eventually able to get started playing with the throttle. It ran rough but eventually evened out.

    I checked the ECU via OBDII and Torque. The TPS is suspect as the "gauge" is not moving in sync with the throttle. I checked the resistance on the TPS terminals and it matches that of my 97. The 97 show proper OBDII gauge movement with the throttle. My 96 seems stuck and random.

    The throttle does work and engine responds, but the ECU feedback is not correct. It is showing 45% at idle and is not moving up or down with the throttle.

    Question 1: Should the car be able to run in this condition? It appears the ECU is not really looking a the TPS signal as the car is running, although the A/F is oscillating nicely.

    Question 2: Does the FFS fuel card do anything the the TPS signal?

    I think I will swap the TPS between the two cars to verify that is is not the TPS.

    Next I think I need to check the voltage at the ECU and verify its to spec. Assuming the TPS swap and the voltage at the ECU are correct, what are the chances its the ECU circuit?

    I just tried starting the car again and it started right up. I am stumped as to why it was so hard to start, then once it did start, it restarts fine.
    96 Montego - FFS ColdSide, 97 Black & Tan, 90 White
    www.miatacare.com

  • #2
    Once upon a time the FFS card modified the signal from the TPS in boost. See if there are wires connected to 3F at the harness.

    http://www.fastforwardsuperchargers....-97-Wiring.jpg
    sigpic


    1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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    • #3
      I have been out driving the car and all seems fine. Whatever it was self healed... That's good and bad. I would really like to know what happened...


      I will probably wait and see if there is a reoccurrence of the problem before messing further.

      Maybe some water in the fuel line. It's running great now.
      96 Montego - FFS ColdSide, 97 Black & Tan, 90 White
      www.miatacare.com

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      • #4
        Keep us posted if it comes back.
        sigpic


        1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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