TFI module goes up in smoke

Discussion in '94-95 5.0 - Specific' started by TX_Snake, Oct 18, 2014.

  1. TX_Snake

    TX_Snake New Member

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    94 cobra I just bought. It was running fine for a few days but just suddenly died. Found TFI was bad. I replaced it and the car fired up, but the TFI module immediately goes up in smoke. Car is stock except for a MSD coil and distributer cap/wires.

    Has as anyone had a TFI literally smoke? Could a bad ground kill it instantly?
     
  2. TX_Snake

    TX_Snake New Member

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    Is it possible for a bad PIP/distributor to instantly fry a TFI module?
     
  3. CC'S95GT

    CC'S95GT Legend

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    I haven't actually seen it.
    I've had the upper bushing in the dizzy get so loose that the reluctor wheel hit the PIP but it didn't fry the TFI module.
     
  4. yzfr6i

    yzfr6i New Member

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    Did you put a thin coat of dielectric grease on the new TFI before you installed it? I've had my PIP go bad as well and it didn't hurt my TFI.
     
  5. TX_Snake

    TX_Snake New Member

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    No, I used thermal paste. Dielectric grease doesn't transfer heat from the module to the heat sink.
     
  6. toyman

    toyman Active Member

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    Sounds to me like there is a short sending 12v to the module. If that's the case it may be in the harness or the PCM.
     
  7. Kboss87

    Kboss87 Member

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    Was it a parts store TFI or a motorcraft? I replaced my TFI with a parts store unit and it poorly. Put a new motorcraft one in and it ran great.
     
  8. TX_Snake

    TX_Snake New Member

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    I got another harness, pulling intake to swap harnesses this morning.
     
  9. ttocs

    ttocs Legend

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    is it possible you got a little messy with the thermal paste and shorted out some of the connections?
     
  10. TX_Snake

    TX_Snake New Member

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    Possible, but I only put TP on the back of the TFI module. Just a thin layer.
    I think the Hall effect sensor in the distributor is bad, causing it to ground to the TFI module. Too much resistance and the TFI module dies and let's the magic smoke out so the won't run. Gonna swap distributors and see what happens.
     
  11. ttocs

    ttocs Legend

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    Its been a long time since I heard anything good about msd dist.
     
  12. CC'S95GT

    CC'S95GT Legend

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    wrong thread oops
     
  13. SLOW95GTS

    SLOW95GTS Active Member

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    Check your grounds.
     
  14. TX_Snake

    TX_Snake New Member

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    New dist and it still killed a TFI module. Gonna chase all the grounds down tomorrow. It is either that it a short in a wire.

    Old dist did have a melted wire in the connector though...that can't be good.

    Stupid project car.
     
  15. ttocs

    ttocs Legend

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    I am curious why your not blowing a fuse rather them smoking the module. If its properly fused it should not let any smoke out even if you short it out. Start at the dist and trace the wires back. Look for the SMALLEST bit of copper that is showing and be sure to insulate any metal showing.
     
  16. TX_Snake

    TX_Snake New Member

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    Got it running! After almost 2wks at the shop I drove it home tonight. Thanks for the help guys, your input helped me get a handle on this issue and get it corrected.

    2nd day after I bought the car, it stopped running while driving home. Towed back to my shop and started looking into it the next day. found a TFI module completely fried, side melted out of it. Started tracing wires, checking resistance/voltage, grounds, etc. More I dug into it more I realized I had a major wiring issue, a squirell had been living under the intake judging by all the acorns/berries/insulation there....and chewed up wires. I ran out of ideas, so I had a electrical specialist come out before and after I swapped injector wiring harness. He then checked/rechecked all grounds/circuits related to that harness. found the PO had wired the fan into the CCRM to be on all the time as soon as you turned on the ign. This was the root cause of the issue. As soon as the wire was disconnected, the fault was gone, reconnected wire, fault was present. buttoned the car back up, broke, then fixed, some vacuum lines, retimed (swapped distributors thinking it was a bad Hall effect sensor), and now it runs great. I get to finally wash it tomorrow and see how well it will clean up. Thanks guys for the help, I appreciate it.