Electrical Questions On Putting '90 5.0 Into '88 5.0 Car

Discussion in 'Fox 5.0 Mustang Tech' started by GT80, Jun 19, 2014.

  1. Ok, so I've been reading up a lot lately on the differences between wiring harnesses between years and there is almost too much info out there. I'm told this is a very easy thing to do compared to a 2.3 to 5.0 swap so I'm hoping there are some quick and easy answers out there. I know most folks would just dive right in but I'm just one of those people that wants to know exactly what I need to do before I get started.

    Here's what I have:

    1990 LX 5.0 5spd hatch with a good engine/tranny. Runs perfect, drive it all the time.
    1988 LX coupe (5.0 5spd car) with engine/tranny and computer removed. As far as I know everything else is there.

    What wiring will I need to take from the '90 when I move the engine over to the '88? If I have to swap every wire in the car I can do that, I just want to know what I'm getting into before I start. Thanks for any and all help.
  2. Why are you considering doing any wiring? Is the 88 harness bad?
  3. Pretty sure I can't just drop that '90 motor and computer in there and just plug everything in but I'd be glad if you could tell me I was wrong about that. Would save a lot of headache.
  4. if the 88 is speed density then you will need to move the maf harness iy is fairly simple and there is plenty of write ups on it.. that should be it sir.
  5. Reading through this writeup I notice in #4 under mass air and engine harness he says that the 90 harness won't work in other years because of the different wiring of two 8-pin connectors by the brake booster. Is this right? Can those connectors be rewired to work? I know there are also the added air bag connectors but I figured those could just be left unconnected.
  6. Why even go that far??

    MECHANICALLY, there is not much that is different between the 1988 drivetrain and 1990 drivetrain. All you need to do is take the engine and tranny out of the 90 and put it into the 1988. Then, wire it like you would if you took the 1988 engine out, looked at it for 5 mins, and then put it back into the car.

    You'll plug all the 1988 wiring connectors into the 1990's sensors like ECT, injectors, etc. The only sensor that won't have a wire is the MAF sensor, but just leave it alone or install a 1988 air tube. Run the 1988 computer as well.

    You are overthinking the swap when all you are really doing is taking a 5.0 engine and putting it into an 1988.
  7. Yeah that's what I'm saying. There is alreaady enough to deal with doing just a motor swap. If it was me, I would get the car running the existing way with the new engine, then tackle a maf or harness swap after you got it right.
  8. Even if you wanted maf just buy the kit that splices into the harness
  9. There is no computer in the '88 so I'll be using the '90 computer. I also want it to be mass air. Would it not be better to go ahead and run that wiring before putting the engine in?
  10. Yeah, good point. Then I just need to bring the computer over from the '90, right? Forgive me if I seem a bit dense on this. I love mechanical work but electrical just isn't my forte.
  11. You'd have to swap the entire engine and body harness over. The 90 engine harness will not mate with the 88 body harness.

    Easier way...

    Use all the 1988 wiring, put in the 1990 computer and do the MAF conversion using the IST harness
    Scroll down about 1/2 way


    Search for mass air conversion instructions to see what pins you'd swap out as well.
  12. :nice:Got it. Thanks!