BOXSMJ Posted April 27, 2009 Share Posted April 27, 2009 so i have a 87 2wd 4.0 comanche five speed and i picked up a 91 4.0 HO motor that i would like to put in it but i can't find any good wright ups. Link to comment Share on other sites More sharing options...
Red 1989 MJ Posted April 27, 2009 Share Posted April 27, 2009 Welcome to the club :cheers: The 87-90 was RENIX computer. The 91-92 was Chrysler. You will have to swap all electrical, to make that work. I think somebody have done that here. Link to comment Share on other sites More sharing options...
Pete M Posted April 27, 2009 Share Posted April 27, 2009 Is there something wrong with your current four-oh? Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 27, 2009 Share Posted April 27, 2009 search "H.O. conversion" using the search feature. this has been done many times. I did it, fairly straight forward. but you'll need to swap all electrical, fuel sending unit, gauges, all electrical components to make it work like a H.O. you can adapt a renix (87-90) throttle position sensor to fit on a H.O. (91+) throttle body, and put a renix distributor, fuel rail, fuel injectors, and CPS with the motor and it will run, but you'll have to do an EGR delete on it and it will no longer have a knock sensor. this may effect your check engine light, and you may not make it through emissions (if you even have to) w/o the egr. Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 27, 2009 Author Share Posted April 27, 2009 the motor thats in in dose nt run right when takes off it falls on it face but slowly picks up and gose normal after about 45mph so i just want to swap it for the power!!!! of the HO Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 27, 2009 Share Posted April 27, 2009 the motor thats in in dose nt run right when takes off it falls on it face but slowly picks up and gose normal after about 45mph so i just want to swap it for the power!!!! of the HO that's really not a good reason. the power differences are minimal (like 5hp if that). if you're wanting true HO, you're gonna need a complete donor vehicle. Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 27, 2009 Author Share Posted April 27, 2009 i have the 91 motor/ wire harness/ tranny what else would i need then? Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 27, 2009 Share Posted April 27, 2009 i have the 91 motor/ wire harness/ tranny what else would i need then? do you have the complete engine bay AND interior harness? gauge cluster? all other little odds and ends electrical related for the inside? do you have the open cooling radiator? cooling lines? vacuum harness? engine computer, all sensors on engine and trans, etc. including speedo sensor? do you have the transfercase for the 91? those are different input spline (23 spline), so your old one (21 spline) won't work Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 27, 2009 Author Share Posted April 27, 2009 yes i have a hole running xj for my parts rig Link to comment Share on other sites More sharing options...
JeepcoMJ Posted April 27, 2009 Share Posted April 27, 2009 yes i have a hole running xj for my parts rig perfect. it will all bolt in, except you will need an MJ 4.0 HO sending unit for the fuel tank. Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 27, 2009 Author Share Posted April 27, 2009 WHERE CAN I GRT THAT? Link to comment Share on other sites More sharing options...
mvusse Posted April 27, 2009 Share Posted April 27, 2009 Please, not so loud. Junk yard. Parts stores say they have them. Parts stores are wrong. Parts stores will sell you a Cherokee unit, saying it will interchange. It will not. They are mirror image. Link to comment Share on other sites More sharing options...
Pete M Posted April 27, 2009 Share Posted April 27, 2009 What size tires are under the MJ? Link to comment Share on other sites More sharing options...
mvusse Posted April 27, 2009 Share Posted April 27, 2009 I doubt tires will make it "fall on it's face" on take off. I run 33x12.50 with the stock 3.55 axles, Renix 4.0/AW4 and can do a 10' burnout on dry pavement. Link to comment Share on other sites More sharing options...
Pete M Posted April 27, 2009 Share Posted April 27, 2009 But he's got 3.07s and a stick. Whole 'nuther animal. I hated mine when I bumped up to mere 30s. :fs1: Link to comment Share on other sites More sharing options...
Geonovast Posted April 28, 2009 Share Posted April 28, 2009 I just went from 205/75s to 235/75s on 3.07s and while it isn't toooo bad, I'm still looking forward to the 3.55. Well, the front is 3.55 anyway... Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 28, 2009 Author Share Posted April 28, 2009 its all stock.. i was thinking my fuel presure?...its like driveing a badly timed rig Link to comment Share on other sites More sharing options...
mvusse Posted April 28, 2009 Share Posted April 28, 2009 Could be fuel pressure, or flow capacity. Can't hurt to change out the filter and the sock on the pump. Sounds more like an ignition issue, though. Are you sure you're firing on all cylinders? When was the last time you changed distributor cap, rotor, wires and spark plugs? Link to comment Share on other sites More sharing options...
Pete M Posted April 28, 2009 Share Posted April 28, 2009 Did this issue come on gradually or quickly? Link to comment Share on other sites More sharing options...
BOXSMJ Posted April 28, 2009 Author Share Posted April 28, 2009 i just picked it up running like that.. but it has new plugs wires cap roter fuel filter i put cool air intake on it. it revs way up just fine it runs like $#!& under a load but picks up and gose fine Link to comment Share on other sites More sharing options...
Jeepman Posted April 28, 2009 Share Posted April 28, 2009 I would try to figure out why Your Renix Engine is Not performing before going into a engine swap... The Renix 4.0L Engine is said to be 170HP and the 4.0L HO is said to be 190HP... I did the HO swap in my 89 MJ and it was a HUGE seat of your pants difference when compaired to the Renix 4.0L and Both engines had roughly the same KM on them... However I did add a Few extra goodies to my HO swap... By NO means do you need to change out the complete wiring harness, You Can use the HO Engine harness and Just splice it into your Body Harness and If you were to use the complete XJ Harness including the Dash/Gauges then you will have to splice into the Tail light harness or search the Junkyard for a 91-92 MJ rear Tail light harness because it will be different and I know First hand since I had to do Just that which do able but a Pain... And As stated you will require a New sender which your not going to get new so that means you need to find a Junk yard sender or do as I did and buy the New XJ sender and Modify it to become and MJ sender... When Doing a 4.0L engine harness swap there is only a few wires that need to be spliced in allthough it will take you longer to weed out the Wiring that you will not use then splicing in the ones you do use... The wire splicing is not a very hard thing to do unless wiring scares you and if it does I would suggest Just fixing what you have now... Link to comment Share on other sites More sharing options...
BOXSMJ Posted May 7, 2009 Author Share Posted May 7, 2009 my comanche projet well the start of the HO swap http://viewmorepics.myspace.com/index.c ... D=34422363 http://viewmorepics.myspace.com/index.c ... D=34422362 http://viewmorepics.myspace.com/index.c ... D=33766494 http://viewmorepics.myspace.com/index.c ... D=34422627 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now