'88 Bronco II 4.0 swap from 94 Ranger

[Dunk67]

The wife recently picked up an '88 Bronco II which she loves but is underwhelmed by the the 2.9. She wanted a 302, we settled on a 4.0 for ease of install while retaining factory air conditioning. A wrecked '94 Ranger came up for sale locally so we picked up the engine, engine wiring harness, engine bay/ECU harness with relay box, ECU, air box, and M5OD as well. The truck is a 2.9 EFI with A4LD. The goal is to have a more or less new 1988 truck the way it should have been built with a bit more power than they did in '88. A practical daily driver with occasional light trail use.

I an not an EFI kind of guy so while the engine/trans rebuild and swap part of this is straightforward enough, the electrical part to make it run is intimidating when I look at this massive wiring harness laid out on the floor. Granted after staring at it a bit I realized about half the girth of the harness is for headlights and other bits that we'll likely keep the original harness mostly intact for. I could use some help identifying those wires to figure what needs to connect to what. I'll need to pick up a electrical manual for each truck, from reading a few threads it seems they changed wire color and location a lot through the 80s and 90s. Other problems I see are the Bronco II battery and ECU being on the passenger side, while the Ranger had it all on the driver's side. I'd prefer to keep it all factory-ish and as clean as possible,though the Bronco II engine bay is 10 lbs of stuff in a 5 lb bag already. Are the Ford type plugs and crimp terminals available anywhere to build new connectors and harness or to make an adapter harness between the engine bay and body wiring?

The wiring will be the hardest part, but so far as the traditional stuff what should I do for any engine upgrades? I've read the 4.0 heads have thin castings that can crack if overheated like the early 2.8 and 2.9 heads so I'm expecting to rebuild the bottom end and buy new casting heads ready to run. What headers will fit the 4.0 in a Bronco II? Any performance or durability upgrades that are easy to do while it's apart?

 

[broncc]

I tried to take notes on what I did when I did this same swap ('89 not '88) let me see if I can find them...

Best thing you can do is take the dashboard out all the way. It makes adding stuff like cruise(horn relay)/ac/auto4x4 and repinning the bulkhead conector a lot easier and makes the pedal box install a breeze.



One day I'll write it all up maybe. Does anyone update the tech library?

 

[alwaysFlOoReD]

The tech library does get updated. Somewhat sporadically. If you put an article in the "article submissions" forum and @ jim oakes (without the space) he will take a look.

 

[broncc]

Here are my notes for modifying the engine side of the big bulkhead connector that goes above the driver left foot. I wouldn't use it as a guide in its current state but maybe a good idea of how to start and plan. All the connectors are really easy to de-pin. Just pop out the red bit right where the two connectors mate. Then take a straight pick and push away the locking tab that holds each contact crimp in the housing.



It would be ideal to have a really big table for this instead of kneeling on the ground for a couple nights with a spreadsheet and a pen running out of ink.



I think I make it look more complicated then you need it to be. There really are only a few wires you need to swap around in the big bulkhead and few connectors that are located on the driver fender liner. The mess is all from deleting 4wabs and all the power options the bronco doesn't have. You can leave most of it if you don't really care about weight and a little clutter. I rewrapped everything in super 88 so I am really interested to see how that holds up compared to whatever Ford used factory.

@alwaysFlOoReD I had written up an article submission a little while ago about putting 2.3L gears into a 4.0L M5 since several people have talked about it but no one seemed to post the details. I don't know if its worth putting in there I was just unsure of the process. I meant write-up here in the sense of a build thread for my b2.

 

[alwaysFlOoReD]

I'm always interested in how things are done. And putting it in your build thread is good because you can always refer back to it when the memory gets hazy. I know thats helped me in my build.

 

[SenorNoob]

So you're planning to keep the 88 dash?

I doubt the connectors/pins can be had new.

The 94 harness may make things more interesting. But certainly still possible. Does the ECU even sit in the same spot?

You'd be surprised how much is the same wire color. (I think I only found one that was totally different. Using a 91 harness tho.)

 

[Dunk67]

Yes, we will keep the original '88 dash. A friend recently saw a Bronco II of the proper generation in the local junkyard. I was going to go get the engine bay harness or at least enough to make an adapter harness but it's gone now. I can always use the original harness from this truck but I generally prefer to wait until after all work is done to cut/sell/scrap parts from a project like this.

The ECU on the Bronco II is behind the passenger side kick panel. Rangers are behind the driver side kick panel. I'm hoping I can just run the engine harness up the other side and it will fit, if not I'll have to extend wiring or consider finding an Explorer harness, which has the ECU on passenger side like the Bronco II.

Getting close to having to figure this stuff out. Engine is rebuilt and just about done aside from odds and ends like sensors and accessories. I'm considering a BBK 66mm throttle body, if only to not need to clean the original throttle body. I was just going to toss it in the ultrasonic but it has sealed bearings installed in blind holes on either side of the shaft so that probably wouldn't be great unless replacing the bearings. Larger throttle body would be nice, and easy at this point if I just need to remove the upper intake to port match.

I am about ready to pull the transmission apart and figure what parts to order.

How we got it:

Current state of things:

 

[SenorNoob]

Nice looking work there.

 

[CooperH]

How did you go about swapping the wires on the plug in the firewall?