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  1. #1

    Default 1986 Mustang ignition issue??

    I have an '86 5.0/5 speed car and I've been having an intermittent problem with it (my favorite kind of problem...). I am in need of changing the throttle position sensor, but I don't believe this is a related problem. Occasionally the tach wigs out and starts erratically reading 1000-5000 rpm more than the motor is actually running. While it's doing this the car stumbles and makes no power. Usually as quickly as it starts doing this it goes away, but it's left me sit before. If my life depended on me guessing I'd say it's an ignition module problem? What are you guys' thoughts?

    Thanks!
    Last edited by GliDeThuNDeR; 05-27-2018 at 02:07 AM.
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

  2. #2

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    The car has been given a coil, 2 modules, wires, and a distributor in the last 1000 miles or so. Going to try to track down a motorcraft module and see what I can make happen after work. Maybe eventually if I throw enough $ at the problem it will go away.
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

  3. #3

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    Did the modules fix the problem when you put them on?

  4. #4

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    Threw a new module in. Problem seems to have gone away. Hopefully my car doesnt think modules are a consumable.
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

  5. #5

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    Quote Originally Posted by GliDeThuNDeR View Post
    Threw a new module in. Problem seems to have gone away. Hopefully my car doesnt think modules are a consumable.


    I would double check your body and engine to body grounds,you may have a problem there causing the boxes to eat themselves

  6. #6
    FEP Senior Member
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    Dec 2016
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    Grand Rapids, MI
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    721

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    I had a somewhat similar issue on my wagon, but it would only act up after 2+ hours of driving which made it difficult to troubleshoot. I wound up replacing the distributor, ICM, and coil with Motorcraft parts. I also remote mounted my ICM onto the driver's fenderwell to get it away from the heat of the distributor. No issues yet, but I've only been driving it around town so far. From doing some research none of the cheap (or expensive ones for that matter) aftermarket ICM's have a good reputation.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  7. #7
    FEP Power Member Ourobos's Avatar
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    Apr 2008
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    Waikoloa , Hawaii
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    1,879

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    Had a similar issue on my 86, except RPM would dip to 200-300 then back up randomly. Tried to TFI modules, but not Motorcraft. Help briefly. Issue returned. Used a motorcraft TFI, problem solved.
    1986 CHP SSP Coupe

  8. #8

    Default

    It's interesting that you mention a grounding issue. I had an issue that was two fold a little over a year ago. The engine to body ground was bad, and the ECU ground was bad. The result was a vehicle that would blow the fuse (originally a fuse-able link) for the ECU and leave the car sit every 2-40 miles. We grounded the ECU straight to the battery and redid some of the other grounds. May need to revisit this if these issues continue. Hopefully now that I have a Motorcraft module, it'll be cured, like in Ourobos' case. Gotta love 30 year old wiring problems
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

  9. #9

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    My radiator isn't in the best shape, and my motor is running a little on the hot side as a result. I wonder if this is a contributing factor? (Going to get temps under control either way, just interesting to consider)
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

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