BroncoII4x4.com

O.k., a lot of you probley know I ended up putting another 2.9L engine in my 1988 Bronco II this summer because we couldn't diagnose the power problems we were having. Well, as luck would have it, I drove about 700 miles on the replacement engine and now it is knocking so bad I fear it will throw a rod. Needless to say I am done with the 2.9 engines and now am going to do it right and put the 4.0 in. I have done extensive research including on this forum and still have a couple of questions. Some people say you can splice the wiring harnesses together while others say to replace the entire thing. What is the best way to do this and do you have to take apart the entire dash for your guages or can you just splice into the wiring? I think I have the rest down, I know you have to use the 4.0 starter and I am told the motor will bolt right to my a4ld transmission. I apologize for another post on the 4.0 but when I do a topic search it pulls up so many pages that aren't even related to the subject that I would be reading all day to find them.

One other question I just thought of. Will my exhaust y-pipe bolt up to the 4.0 engine manifolds? Again, some say they will and other say they don't. I just spent $400 on having a dual exhast system fabricated and hope it will still work. I have the factory y-pipe with the cats and a quality muffler that has two outlets where my duals start and run straight out under the rear bumper.

Check out therangerstation.com on there you can find all you need for the swap. All I know is if you have a EFI B2 then a 91 or 92 Exploder motor will bolt right in.

it depends what your 4.0L came out of

The 4.0 came out of a 1994 Explorer.

For the most part, the computer engine and harness is self contained system. You just need to splice a few wires... key on power, crank, fuel pump etc. Break it down into individual pieces and take it one wire at a time.

Also check out DBrowns writeup.

http://www.broncoii4x4.com/4.0L-swap/4.0L-swap.php

I think those manifolds will boltup mine was from an areostar so they did not.

i changed mine out of an 1991 explorer and put it into an 89 BII everything bolted right in beautifully right down to using the motor mounts off the 2.9 on the drivers side instead of using the busted one that was on the 4.0. it all boplted in on mine and i used my y pipe off the 89, but i hear the 89 and 88 models were different exhausts.