1G swap 4G37 with 4G63 n/t - wiring/harness

Posted by sacrileger, May 15, 2018

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  1. sacrileger

    sacrileger Proven Member

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    Orillia, ON, Canada
    I am taking my 4g37 engine from a 1990 Laser and replacing it with a 4g63 n/t 6-bolt motor from a 1992 Talon. The '90 Laser has no A/C, cruise, etc. The Talon does. I already took both engines out and noticed that some of the connectors dont match up, i.e. the O2 sensor. I figured I might as well swap the engine bay harness - just to be sure. And here I ran into a problem. I am trying to unplug the harness from the interior harness at the firewall on passenger side. The plug says "push" so I am "pulling" and turning to dislodge it with no success. I am hoping to plug the 4g63 harness to the interior 4g37 harness at the firewall. I searched a few post and it would appear that once I swap the ECU, and apparently the cluster as well, sigh :( , I dont need to do anything else on the inside since I am not installing A/C and/or cruise control. Any idea as to what the secret password for unplugging the harness just at the firewall is? I am attaching a pic of the "plug/connector" IMG_0456.JPG


    as well as some additional pics for you guys who enjoywatching garage porn.
    IMG_0447.JPG IMG_0448.JPG IMG_0449.JPG IMG_0450.JPG IMG_0451.JPG
     

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  2. BoostedTalonTS

    BoostedTalonTS Proven Member

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    Bay Area, California
    There are a few tabs that secure an inner plastic retainer that's right behind the rubber grommet material... gently pry the rubber around from the back of this white plastic liner, and you'll see the clips that help hold it to the firewall. These clips push towards the center of the plug, to release it
     
    My DSM:
    1994 Eagle Talon TSi AWD

    12.760 @ 112.400 MPH
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  3. brian9397gsx

    brian9397gsx Proven Member

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    sioux city, Iowa
    You can pull the rubber back from the inner plastic retainer. It has a rim around it that keeps it tight and two longer tails that go further down the harness inside that are taped to the wiring to secure it. But you just have to pull it off the rim enough to get at the plastic lock tabs.
     
    My DSM:
    brian9397gsx 1993 Mitsubishi Eclipse GSX

    19.80 @ 35.55 MPH
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  4. sacrileger

    sacrileger Proven Member

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    Orillia, ON, Canada
    thank you for replies above. I have pulled the rubber back but I still cannot see the male/female connector that separates the engine bay harness from the interior harness. Can the connector/plug be accessed from outside? I looked underneath the glove box and did not see anything that can be disconnected at the firewall so that I can pull the engine bay harness out.
     
  5. BoostedTalonTS

    BoostedTalonTS Proven Member

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    It's not a connector, at the firewall location, but only a place where the harness passes through it... you will need to dig deeper to find where the harness terminates, at the various locations, with the majority of them being at the ECU and/or TCU (if equipped)
     
    My DSM:
    1994 Eagle Talon TSi AWD

    12.760 @ 112.400 MPH
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  6. AllanL

    AllanL Proven Member

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    LV, Nevada
    the connectors are a little higher up the under dash.

    just removing the glove box usually won't do. it is even higher than where the AC unit sits under the dash.
     
  7. sacrileger

    sacrileger Proven Member

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    Orillia, ON, Canada
    That's nuts!! Other cars I worked on terminate the engine bay harness at the firewall with a male/female connector.
    Can this be done without taking off the entire dashboard? Is this the best one can do for 1G or is there a better way?
    1g engine harness removal
     
  8. mitsubishikid

    mitsubishikid Proven Member

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    Turlock, California
    you won't have to pull the dash to get the engine harness out, I have pulled many of these out, but the heater box has to come out at the least, and you might have to loosen the a/c evaporator box, if it's a/c is discharged I'd pull it out... I happen to have a full harness that I'm working on so heres some pictures of all the connectors on the dash side of that firewall grommet, I count 12 connectors including the ground ring terminal that gets bolted to the stereo frame [my harness is an automatic if yours is a 5 speed you will have a few less connectors].
     

    Attached Files:

    Last edited: May 16, 2018
    My DSM:
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  9. sacrileger

    sacrileger Proven Member

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    Orillia, ON, Canada
    That looks great! I gather from your description that the engine harness ends at the ECU and console? Instead of behind the dashboard/instrument cluster?
     
  10. mitsubishikid

    mitsubishikid Proven Member

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    Turlock, California
    Yes, but there are about 3 plugs that are in the passenger side kick panel that go under the dash but because they have connectors you can unplug the dash from the harness.
     
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  11. sacrileger

    sacrileger Proven Member

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    Orillia, ON, Canada
    ok, I'll give it a try. thanks.
     
  12. kronus

    kronus Proven Member

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    Joined Jan 15, 2006
    Provo, Utah
    I did this swap many years ago, but swapped to the turbo engine. It is possible to swap the harnesses without pulling the dash as mentioned above, however, after struggling upside down and in a contorted position, I found it easier and more time efficient to pull the dash and then swap the harnesses.
     

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