Fixing Previous Owners 4.0 swap mess

[mjlogan]

Just picked up a very clean '90 ranger that originally was a 2.9/5speed. The previous owner swapped in a 4.0 and gave up once it started "running". Basically hacked the wiring harness and made a mess of it. Welded bungs in the y-pipe for o2 sensors, etc. This is a very clean truck and I want to save it as well as have it pass CA smog.

I am not positive of the year 4.0 it has, but here is what I know

-2 oxygen sensors
-has EGR
-aluminum intake
This leads me to believe i'm working with a '92-93 motor

Here is my plan of attack:

Grab a virgin wiring harness out of the junkyard and do this the right way. This is where I need some advice. Do I:

Option 1:find what year this 4.0 is and use that harness
Option 2: find a harness that would better mesh with the '90 chassis (like a '90 4.0 harness)
Option 3: pick up a 2.9 and just put it back to stock

Option 2 would involve me matching this motor to be just like the truck I scavenge parts off. For example, I get the harness off a '90. It will have one o2 sensor therefore I get the Y-pipe off it as well, and computer etc.

Please correct me if I am mistaken (new to the 4.0 thing) and I am open to any advice. I am also within 20 minutes of 3 huge pick a parts so I am confident I can find nearly any year 4.0 I need to scavenge parts off.

 

[chilsam]

Keep the 4.0

Id use the 2.9 y pipe and pick up underhood harness and sensors from as close a year 4.0 donor truck to yours and the ac condensor and lines are needed also.We did a 91 4.0 auto into a 89 2.9 M50 used the auto harness had to splice nuetral safety and reverse light switch and repin a couple cannon plugs but it is WORTH it.You'll LUV the 4.0!

 

[mjlogan]

Right on, thats what I was planning on. I'm getting rid of all the AC stuff, so that shouldnt be a big deal.

So far the closest I have found a '90 4.0 ranger with an auto, a '91 explorer 5 speed, and a '92 explorer 5 speed. Which of these would be the best bet? I've still got 2 other yards to go through, so i'm hoping to find the exact match I need.

 

[chilsam]

The 90

Id use the 2.9 y pipe and pick up underhood harness and sensors from as close a year 4.0 donor truck to yours and the ac condensor and lines are needed also.We did a 91 4.0 auto into a 89 2.9 M50 used the auto harness had to splice nuetral safety and reverse light switch and repin a couple cannon plugs but it is WORTH it.You'll LUV the 4.0!

We are using the 91 auto ECU also with no probs.Just cant use manual ECU with a auto.The cannon plugs were located on drivers side by the frame rail colors were the same just diff locations,grab the fuel lines,throttle and CC cable also they are diff between 2.9 and 4.0.There is a thread in "OTHER ENGINE SWAP'S" that shows how to mod the 2.9 lines and repin plugs in that forum. GOOD LUCK! I didn't see were the 2.9 y pipe is hacked up grab the 4.0 y pipe their the same.The plug for the O2 sensor might be diff also 4 instead of 3 pin's. I THINK? LOL

 

[disciplerocks]

I bet its a 94 motor since it has egr. But if you can find the whole harness from a vehicle that has egr and the same tranny you have, then you should be golden.

 

[mjlogan]

Picked up a harness from a '90 ranger with a 4.0/auto. My plan for now is to first get the new harness in and clean. I am thinking I am going to have trouble using a non-egr harness with an egr motor. If this is the case then I will just grab an non-egr intake man. and make this motor into a '90.

As far as computers go, I'm going to figure out what year the current computer is and try that out. If it gives me headaches i'll just get a noon-egr computer to match the rest of the swap. Sound like a good plan?

It is my understanding that i shouldnt have to re-pin anything on the drivers side round plug on the firewall since both harness and truck are '90. Thats the main reason I went with a '90 harness. Basically trying to make this as clean and factory as possible to get through emissions.

 

[disciplerocks]

The computer needs to match the harness.

 

[mjlogan]

The computer needs to match the harness.

makes sense. probably should have grabbed the computer out of that truck too...