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Engine revs when ECM / PCM / ECU pushed...

Discussion in 'Stock 1991 - 1994 Explorers' started by Cheddar Dan, August 2, 2017.

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  1. Cheddar Dan

    Cheddar Dan New Member

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    Hmm? My question: What are the vacuum lines next to the ECU, please?

    THANKS!
    .d
     
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  3. Rhett

    Rhett Let Them Eat Cake Elite Explorer

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    There aren't any vac lines next to the ECU. The ECU is in the passenger side kick panel, in the cab.
     
  4. natenkiki2004

    natenkiki2004 Blue Bomb!

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    I think there is one that comes in for the blend doors or AC system.
     
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  5. 2stroke

    2stroke Elite Explorer

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    If there is a vacuum line by the ECU, it would have to be disconnected. I think it goes up behind the glove box. I wonder if you mean the ICM? I think the only vacuum line remotely close to the ICM is the stuff for that thermostatic control on the air box.
     
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  6. Cheddar_Dan

    Cheddar_Dan New Member

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    Thanks, All! I'm referring to the "computer" at the front passenger's right foot.


    ....I was working in that area chemically cleaning connectors and double checking a computer "chip" I installed back in the 90's …as part of my never ending search for CEL fix.


    When the "computer" case was disturbed something in that area caused a sudden rise in RPM's. Could be caused by one of the many wires in that wiring harness, but with a 23-year-old vehicle I am always suspicious of cracked vacuum hoses. That’s why I asked about the mystery vacuum hose.


    Thanks!
     
  7. natenkiki2004

    natenkiki2004 Blue Bomb!

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    I don't think you're in the right area for vacuum lines. There should be one that comes in the firewall above and to the right of the inertia switch but it should go towards the heater controls, not the other way towards the PCM. I'd wonder if you have pin fitment issues or a break in the wiring. That would definitely cause a CEL if it's changing the idle. If you find out what CEL you get and correlate it to a specific sensor, then look up a wiring diagram and see what pins/wires you need to be checking, you should hone in on it pretty quick.
     
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  8. gmbroy

    gmbroy Elite Explorer

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    This is a diagram of the vacuum for the heater & should give you an idea .

    1991 heater vacuum diagram.gif
     
  9. Cheddar Dan

    Cheddar Dan New Member

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    BIG THANKS, ALL!!!!
     

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