the 2.9 in my baby Bronco recently developed terminal problems. Since the engine has so many miles on it, I am considering replacing it with a 4.0 from a 94 Explorer. I believe that everything will fit, but I am concerned about the differences in the wiring harnesses. If anyone has done a swap like this, or knows where to obtain an aftermarket wiring harness, please contact me by email. My address is tinknocker@windstrem.net Any other tips or advive will be appreciated

 

i was considering the same swap with my 87 ranger, my 2.9 has a cracked head, i know the 4.0 is DIS so there will be some differences in the wiring harness, i know the 4.0 has a drive shaft for the oil pump, being a 4.0 is close to a 2.9 ( same firing order, same bellhousing pattern) why not drop the 2.9 distributor in the 4.0, maybe modify the 2.9 wiring harness to fit the 4.0 ( you know, most of the efi control connectors are universal on theses engines)

 

I did a swap - engine was a '90 Rngr I believe and the recipient was a '89 B2. The only problems that I had were some wires in the two harnesses' plugs (the main one at the firewall) were in diff spots.

As I remember there were acouple that were harmless like the speaker wires or something. I think that I had two haynes manuals and just went one by one thru all the wires - if you look closely on the plug (big one @ firewall) it will have a small number at each wire location cast into the plastic. You can take the red(I think) plastic "key" out with a sharp awl and then reach into the plug, dislodge the little plastic finger that is held against the wire receptacle (male or female) by the red key and slide the wire out, then put it into it's new position.

It has been a few years but it was a one-by-one process. I think that ford kept all the same color codes (like the starter kick wire is always reb/blu stripe) but for some reason swapped positions on a few. And the donor didn't have power windows... but... all the wires were there, just add the correct fuses in the power dist box, voila.

Myself, I changed the whole harness complete. Everything. Power distribution box, headlight connectors, all the bolt-on ground connections, the complete harness. When started it was a nightmare of wire harness and connectors dangling everywhere. But, logically you would start at the firewall plug (once you were thru comparing the 2.9's harness to the new one) and work your way around to the other side.

And once I had it all done I tried to fire it up and as the motor had laid around for so long the fuel rail had no fuel in it. So crank... and check... and fool around with changing computers etc. I believe the 2.9 comp will work with the 4.0 also(I think) Then after all my monkeying around... I squirt some gas in the throttle and away we went.

I got way better gas mileage (I think it doesn't work as hard) and a lot of rip for that little Bronco. And it's still hanging around.

Oh yeah, the fuel delivery and return lines were different connectors but that should be no big deal.