Swapping A Different 4.0 Motor Into My '88...

[bumpy]

Hey all, i got this 88 MJ off here a few months ago, it ran well for a few months then took a $#!&... fouled out all the plugs and doesnt have over 75lbs of psi in any cylinder... time for a new motor in my mind..

anyways, i was wondering what other 4.0 motors i coulld swap in WITHOUT too big of a hassle?

i found a 4.0 from a '91 MJ for $225 locally... what all would i need to do to my jeep to get this motor to work in it? I'm sure it can't be as simple as un-doing bolts and swapping everything!? will i need the ecm from the donor vehicle? what else will i need?

also while the motor is out, I'm planning on swapping in a header, the 97+ intake manifold and doing all the wear and tear gaskets that typically fail on the 4.0's... what else should i look for and put my attention to?

I have swapped 3 motors before, all in XJ's, a '99, a '95 and a '92... none were a renix.. the current MJ is a renix, what all does that mean? what can or can't i swap with my current jeep being a renix motor and the new motor not being a renix motor? it just means its a non ho right? with a open cooling system i believe? never have been 100% as to what a renix motor was and included and meant haha...

 

THANKS FOR ANY AND ALL HELP EVERYONE!!!

[hitman72]

I am very new to this but from what i have read. 91 is to new, you will have to swap some of the electrical. 90 to 88 would be a direct swap.

 

(help me out here, i post this to check if my knowledge and make sure i have it all in the right order) haha  

[ftpiercecracker1]

I am very new to this but from what i have read. 91 is to new, you will have to swap some of the electrical. 90 to 88 would be a direct swap.

 

(help me out here, i post this to check if my knowledge and make sure i have it all in the right order) haha  

 

 

 

Doin good so far. :thumbsup:   The 91 will be a HO motor and if its complete; wiring harness, fuel delivery/lines, ECU, Transmission, I would go for it. If you just want straight drop and go, look for a motor between the years listed AND the same tranny.

[hitman72]

and pre 88 would be non renix right? 

[87manche1]

87 is renix. Above 91 at the least you'll need is intakemani complete exhaust all the way to cat, thortle pedal with cable, and adapt the throttle position cable.

[ftpiercecracker1]

86 4.0 was not avaiable, 87-90 is Renix, 91-92 is HO

[cruiser54]

Here's all you need to get the job done:

 

 

 

Cruiser’s HO into Renix Swap

This swap is easier than some will lead you to believe, generally those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

The HO and Renix have some differences but none that can’t be overcome very easily.

Any HO engine from an XJ or ZJ through 1998 can be used. One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from the HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head for the sender.

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use the Renix gasket. Exhaust ports are identical.
You will need to use your Renix distributor as it is different than the HO because they use different fuel management systems. The  flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16” square drive or a modified 3/8” drive that has been ground down to fit. Do this before installing the engine.

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.

Revised 07/24/2012