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Thread: 87 csx Lm pinouts needed

  1. #1
    turbo addict
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    87 csx Lm pinouts needed

    In particular, the TPS return signal wire connector, pin and if possible color and gauge? Thanks in advance. I'm chasing a strange rise in TPS voltage once warm causing an erratic idle and high idle.

  2. #2
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    Re: 87 csx Lm pinouts needed

    Quote Originally Posted by shadow88 View Post
    In particular, the TPS return signal wire connector, pin and if possible color and gauge? Thanks in advance. I'm chasing a strange rise in TPS voltage once warm causing an erratic idle and high idle.
    http://minimopar.net/ecu/lm-1987-t1.html
    I have an FSM as well
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  3. #3
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    Re: 87 csx Lm pinouts needed

    Thank you. I totally forgot minimopar

  4. #4
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    Re: 87 csx Lm pinouts needed

    Ok, I fully have to admit, I was thinking about my issue with this car incorrectly. My problem was related to the ground circuit, not the signal wire, as I first thought. I teed into the ground terminal and gave it a ground at the throttle body mounting stud and all my crazy idle problems are fixed.

    As a lesson, there's 5 volts supplied, a small amount is sent to the LM. In this case about less than a volt at idle. The rest goes to ground. If the ground is dirty, faulty, or corroded, the dirt, corrosion, fault causes resistance and a voltage drop. This voltage drop causes more voltage to travel down the signal wire and mess up your LM readings. Maybe I explained it wrong, but it works that way.

    Any hooo..... I don't have a 1987 service manual, so where is the ground or splice supposed to be for the ground circuit from the TPS? I expect it to affect a few sensors, but I'm only struggling with one right now. TIA!!

  5. #5
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 87 csx Lm pinouts needed

    Is it the black with blue tracer wire? Those have splices in them all over since it's the ground used for almost all the sensors.

  6. #6
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    Re: 87 csx Lm pinouts needed

    Quote Originally Posted by shadow88 View Post
    Ok, I fully have to admit, I was thinking about my issue with this car incorrectly. My problem was related to the ground circuit, not the signal wire, as I first thought. I teed into the ground terminal and gave it a ground at the throttle body mounting stud and all my crazy idle problems are fixed.

    As a lesson, there's 5 volts supplied, a small amount is sent to the LM. In this case about less than a volt at idle. The rest goes to ground. If the ground is dirty, faulty, or corroded, the dirt, corrosion, fault causes resistance and a voltage drop. This voltage drop causes more voltage to travel down the signal wire and mess up your LM readings. Maybe I explained it wrong, but it works that way.

    Any hooo..... I don't have a 1987 service manual, so where is the ground or splice supposed to be for the ground circuit from the TPS? I expect it to affect a few sensors, but I'm only struggling with one right now. TIA!!
    All this stuff is explained by Ohm's law V=IR but the main thing is you figured it out!
    I will check the 87 FSM for location of the ground
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  7. #7
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    Re: 87 csx Lm pinouts needed

    Thanks Miles!! Yeah, I've been through plenty of classroom training on Ohm's law, but I had it in my head, it was induced voltage on the signal wire from an unknown source.... Yeah....I really should know better... The point is, it's figured out, but I would like to know where the problem is, instead of just this patch job.

  8. #8
    Supporting Member II Turbo Mopar Contributor 85lebaront2's Avatar
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    Re: 87 csx Lm pinouts needed

    I do have a 1987 FSM set and can scan what you need, posting it on here might be an issue as the scans are PDF format.
    "growing old is inevitable, growing up is optional"
    1986 Lebaron convertible to replace totalled 85
    1986 Ford F350 Crew Cab DRW
    1995 Lincoln Continental (project car)
    2011 Ford Flex Limited (wife's)

  9. #9
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    Re: 87 csx Lm pinouts needed

    Quote Originally Posted by 85lebaront2 View Post
    I do have a 1987 FSM set and can scan what you need, posting it on here might be an issue as the scans are PDF format.
    If you would please scan and email to shadowman1518@outlook.com ... I would like to see the ground wire and splice locations for the tps wiring.

  10. #10
    Supporting Member II Turbo Mopar Contributor
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    Re: 87 csx Lm pinouts needed

    Jamie file sent
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  11. #11
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    Re: 87 csx Lm pinouts needed

    Thank you very much, Miles.

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