Difference in 4.0's 89-96

Badcop · Sep 19, 2005

I have my stroked 4.6 in whats left of my 96 chassis, I now have a gutless 4.0 in my 89'. I will be swapping when the harness from Hescos shows up and time allows.

HOWEVER, I have another 96 4.0 on the engine stand and was going to swap a few parts till Im prepared to do the full swap this winter.

When it comes to head, intake, fuel and exhaust, there all the same right? The big exception being the fuel injection vs. TBI injection. Ive already noticed that after my serp blew yesterday throwing my fan all out of wack, there is an additional pulley on the newer engines that the older ones did not have.

Other than that Im fairly confident that there are no other major differences. I will be trying the head and intake swap this afternoon. Is there anything I should be aware of from those who have the older engines and have done some of this before?

Brian

summitlt · Sep 19, 2005

The intake and exhaust are different, need to use both from one engine. Both are a "multiport" fuel injection. 96 would be chrysers version, 89 would be the Renix version.

The HO has a different cam (I think) different head, and some other minor stuff.

Badcop · Sep 19, 2005

will the head fit with the renix intake and exhaust, and will the mpi mate to the ho head?

Badcop · Sep 20, 2005

Just in case anyone else would like to know:

Head is interchangeable, the 96 head has a larger valve opening.

Intake is also, and flows alot nicer even with the TBI form the 89 on it.

Injectors are the same from CPU and TBI.

Waterpump, and a whole lot more.

After I swapped it all over last night, it runs better than I could have ever imagined with an odo of 225k +

jfiscus · Sep 20, 2005

If you're gonna just swap from the head up I hear it's not that bad.

I just swapped in a whole 93 block into my 89 and kept my 89 wiring harness/sensors. You have to modify these and some more parts:
Exhaust manifold angles are different (and bolt up differently to the blocks)
TPS sensors are different. If you're using the new intake you'll have to 'rig up' the TPS.
You'll have to use the CPS from the 89.
Fuel lines run differently, you'll have to extend the 89s lines to both run to the front of the engine.
AC/Alt & brackets are different, you'll have to put the 89 parts on the newer engine.
Coil & Distributor are different, you'll have to put the 89 ones on the new engine.
Throttle cable, tranny kickdown cable both need to come from the newer engine if you're using the newer intake.
Oil pump will need to be used from the old engine.
I was able to unscrew all of my engine sensors from my 89 block and screw them into the newer block.
You'll need to use the newer style airbox with the newer engine.
Vacuum lines are going to be tricky.
There's probably some other pieces I left out in this post and some other problems/challenges you'll encounter with a 96 & newer block.
I get around 10 mpg with stock gears and 33s with my new engine. I believe I still have some sensors wrong or vacuum lines that would improve my mpg.

Badcop · Sep 20, 2005

jfiscus said:
If you're gonna just swap from the head up I hear it's not that bad.

1. TPS sensors are different. If you're using the new intake you'll have to 'rig up' the TPS.

2. You'll need to use the newer style airbox with the newer engine.

3. Vacuum lines are going to be tricky.

Heres the solutions I used for those problems:

1. Insert a 15amp fuse into the plug, It will fool the computer into thinking it has a full loop.

2. Eliminate the problem completely and order a 40$ K&N from rustys.

3. Take the vacuum bottle out of the bumper form the donor and install it where the old air box was, link te missing air tubes into it to fool eachother.

xjnick · Oct 3, 2005

Badcop said:
Heres the solutions I used for those problems:

1. Insert a 15amp fuse into the plug, It will fool the computer into thinking it has a full loop.
QUOTE]

\

back up a second. explain that one, which computer are you talking about? using a new tps on the old computer?

jfiscus · Oct 4, 2005

Badcop said:
Heres the solutions I used for those problems:
1. Insert a 15amp fuse into the plug, It will fool the computer into thinking it has a full loop.

How would it sense the Throttle position from a fuse?

I used the old TPS cut down to mate with the new intake butterfly shaft piece. I notched the old TPS to become a female and used spacers and longer bolts to hold it on. It was very finicky about how it ran if the TPS was not in the right position in relation to idle to wide open positions and made idle/gas mileage very greatly.

ECU88XJ · Oct 4, 2005

Badcop said:
Just in case anyone else would like to know:

Intake is also, and flows alot nicer even with the TBI form the 89 on it.

Injectors are the same from CPU and TBI.

Waterpump, and a whole lot more.

Just so there's no confusion here, there was never TBI (throttle body injection) on a 4.0 in the cherokee.

The renix fuel injection system was used from 87-90 and from 91 on they used the chrysler Engine management system and called it the 'HO' (high output) engine.

Both systems are multiport systems with 6 individual injectors plumbed into the intake.

It is my understanding that the Intake and exhauyst runners in the head were bored out more in the HO engine than the renix.

I believe, someone confirm please, that the HO motor would be a direct bolt in if you retained the renix intakemanifold and throttle body and all associated sensors and the renix exhaust manifold.

Using the HO intake and throttle body should require electrical / computer mods.

jpnjim · Oct 4, 2005

I put a 92 (YJ) 4.0L into my 88' MJ (tech stuff here:
http://www.jeepsunlimited.com/forums/showthread.php?t=675004 )

BTW, 96 vs 88' 4.0L's

block is the same (though 96 has a main bearing girdle added)
Crank & rods are the same

Engine management system completely different

91+ head revised, bigger, higher intake ports (87-90 was a semi-high port compared to the old 258's, with a 'dog leg' for the injectors).
Intake different, 91+ throttle body bigger, 91+ exhaust better flowing (& EGR deleted)

Pistons were redesigned
Cam is different (96' has smaller exhaust to recover some low end torque lost in 91')
Alternator is different ( 91+ voltage regulator is part of the engine controller)
Throttle cable is different for new TB

jpnjim · Oct 5, 2005

I didn't think of it the first time,

but the injectors & fuel rail are different 96+, and probably won't work as well as the early HO setup did for me.

The same question was just asked here:
http://www.jeepsunlimited.com/forums/showthread.php?p=5881247#post5881247

jpnjim said:
http://www.jeep4.0performance.4mg.com/tech_specs.html

Looks like 96' injectors flow 23.2lb/hr at 49psi.

At the stock 39psi your fuel pump usually supplies, the injectors will flow less than the 23.3lbs.
I don't know the formula Dino uses to figure the flow at the lower psi, but the injectors may, or may not be big enough at the lower psi.

I'm running the stock 91-93 style 21psi injectors, and they seem to be a good combo for this setup.

I guess you could either:

get 91-95 injectors & rail

keep the lower flowing 96' injectors (depending on what they flow @ 39psi), with a 91-95 rail

swap your lower flowing 18.6 lb/hr 87-90 injectors in, with a 91-95 rail

or swap in a 96+ 49psi pump.

I'd probably go with the 91-95 injectors + rail.

Difference in 4.0's 89-96

Badcop

NAXJA Forum User

summitlt

NAXJA Forum User

Badcop

NAXJA Forum User

Badcop

NAXJA Forum User

jfiscus

NAXJA Forum User

Badcop

NAXJA Forum User

xjnick

NAXJA Forum User

jfiscus

NAXJA Forum User

ECU88XJ

NAXJA Forum User

jpnjim

NAXJA Forum User

jpnjim

NAXJA Forum User

Similar threads