JeepDeepInIt

So, right off the bat I have a 91 laredo that was rear ended(while parked) on 4th of july. the accident didnt do too much body/frame damage to ol' jeepy. (shoulda seen the other guys crown victoria!) anyway, i thought it was too good to be true which it was. two days after the wreck, im getting out onto the interstate when KABANG! the transfer case literally snapped in half (not along the seam either), front driveshaft swung up and busted a couple fuel lines and what not.

i get it towed, and call a buddy of mine for a favor. he had a 1990 limited laying around in his boneyard with a junk engine in it. so, knowing my motor was still good and liking the look of the limited vs laredo, i embarked on an adventure to swap engines. i pulled the motor, trans and xfer case all at once out of both jeeps. only took about 2.5 hours each (not bad for it being the first time i ever wrenched on a jeep other than starter replacement) unbolted the 1991 4.0L High Output from transmission. same for the 1990 4.0L non HO. bolted the HO up to the good trans, and xfer case. dropped 91 HO into 90 body no prob. slammed it home first try. went to begin pluggin in wire harness's and thats when it hit me. the wiring was completely different except for a couple here and there. got to work taking sensors off non ho motor, put them into ho motor. switched distributor and alternator (and brackets! for heaven sake). throttle position sensor had different harness so, i tied the harness from the 91 laredo into the mix. everything plugged in, and accounted for.

engine turns over, but no spark.

i wish i would have replaced the CPS before putting the new engine in.

long story short here. has anyone ever attempted to replace a 4.0L engine with a 4.0L High Output engine ? if so, did i fudge up somewhere along the way?

EDIT:

forgot to add: no check engine light!
tried using coil from 91HO motor, no spark + different harness.
any input appreciated greatly!

JeepDeepInIt

so after a few hours perusing the site, i found some helpful links. learned some lingo.

i attempted to put a 91HO into a renix ready vehicle. i may need to buy the book before i get my rig up and running. still looking for advice. if all goes well, i may post a write up for the next guy diving right into the ball of wax im stuck in at the moment.

1990cherokee

when i blew my head on my stock 4.0 i went and bought a H.O 4.0 head from a junk yard and installed it, very nice power and i love it.

JeepDeepInIt

well, i guess the tech specs book is going to be the only answer for me. even then, i still need to replace the CPS most likely. too dark tonight first light tomorrow.

troy0873

hey how are you? i might be diving in to this soon myself...so you changed a 4.0 renix to a 4.0 h.o.? that is i'm planing...was wondering if you got it running and can you give me any pointers?

JeepDeepInIt

no it is not running as of right now, the engine turns by key but wont start up.

rweaver138

PICS!!

Lets_Ride_all

I have just done the engine swap and am also still having problems. Mine now starts, idles. It does not always start though and the alternator is not working. How do you wire up the HO alternator with the 90 harness? I have tried it a few different ways and the display does not change and the battery dies after it runs for about 10 min. Also is the idle control motor different wiring on the HO engine? It wouldn't idle until I put my 90 IAC into the 92 donor engine I have. This got it to idle correctly.

The final problem I am working on is shifting, it won't shift into 2nd, 3rd 4th until about 5K on the tach. I am thinking this is due to the cable adjustment going to the tranny.

JerseyJeeper

Lets_Ride_all

The transmission isn't shifting because the original throttle body has 2 outputs. One for the transmission and one for the engine ECM. As far as starting I found my rotor was in 180 degrees backwards. With all the changes I made though I went through a lot of checking.

jarretthise

Why didn't you just pull the complete motor harness and swap them? I would have gotten rid of that renix harness altogether. Just because you swapped plugs and what not doesn't mean it will solve a thing. Different years get their power sources from different wires and places.