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Cat ECU... again I suspect!

Discussion in 'Mondial' started by greatscott73, Jul 5, 2019.

  1. greatscott73

    greatscott73 Karting

    Sep 1, 2017
    185
    West central Florida
    Full Name:
    Howard Scott
    While poking around in my recently purchased 87 3.2 cab, I noticed a four prong connector going to the cat ECU in the right rear of the car. The connector had been disconnected from the harness and was just hanging there. Thinking this couldn't possibly be correct, I reconnected the four prongs. The next time I drove the car ( which was previously running just fine) it seemed a bit sluggish and the "Slow Down" light was intermittently coming on and off. I have read about bad thermocouples and ECU boxes, but is it really just as easy as disconnecting the ECU from the harness to eliminate the problem? I have a new thermocouple laying around that I may install and see what happens, but that is a rather expensive piece if not really needed. All sage advice will be appreciated!
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,976
    Texas
    Full Name:
    Steve Magnusson
    There's no "intelligent" connection between the cat ECU and the engine systems on your model -- so no effect on engine running whether plugged in or not. Since you haven't gone up in flames, most likely the cat ECU was unplugged for giving false indications. When unplugged, the only difference would be the self-test would not work when first turning the key "on". Does the self-test work well, and always, when you have it plugged in? If not, that's a good reason to replace it.
     
  3. greatscott73

    greatscott73 Karting

    Sep 1, 2017
    185
    West central Florida
    Full Name:
    Howard Scott
    The self test lamp never lit until I plugged it in. Then it did. I just went out and swapped out the thermocouple and all seems to be operating as designed, so I guess I will leave it plugged in if it doesn't cause any more issues. That whole "going up in flames" thing doesn't sound like much fun. Thanks for the quick reply Steve. Your knowledge is highly appreciated!
     
  4. davebdave

    davebdave Formula 3
    Silver Subscribed Owner

    Mar 18, 2007
    2,372
    Northern VA
    Full Name:
    Dave W
    I replaced both in our t years ago. If I get another failure they are going in the trash and I’ll install an Exhaust Temperature Gage instead.
     
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