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Engine Swap Questions

T

Tyj99xj

NAXJA Forum User
Location
Cashmere, WA
I have a '99 XJ w/ blown motor and a '90 MJ, both with the 4.0L

The 4.0L in the MJ is a HO because it was swapped with all the wiring from a '93 XJ, now I am looking to rebuild this motor.


Here's my question, if I go about rebuilding the '93 HO will I be able to use all of the wiring/sensors/dash from the '99 in my MJ?

Basically, I want to rebuild the '93 motor, and while it is out swap everything from the '99 such as dash, interior, wiring, etc. Once the '93 motor is rebuilt can I just drop it in fire it up or am I going to have to do a bunch of work with the connectors and everything? Any help would be greatly appreciated.
 
99 is an ODB-II, 93 is an OBD-I. That alone may cause you some grief.
 
True. As long as you're swapping everything, sure.
 
I think you will find a number of minor annoying differences you will need to deal with.
 
You will have to remove anything and everything that is 1990 and replace it with equivalent 1997-01 parts.

Some from this one (90), and some from that one (99), won't work.
 
Some 90 parts may work but others won't.

Just so we're all clear (I know I'm not) - 90 MJ with 93 XJ electronics, still has 90 MJ longblock, or did you swap the 93 XJ longblock? I forget how the late model intake lines up with the ports on the RENIX cylinder head. IIRC it will line up fine on the 93 cylinder head though...

You are also looking at some sheetmetal work on the firewall to make the newer interior parts line up well with it, but from what I've seen on various build threads it's not too too bad.
 
kastein said:
Some 90 parts may work but others won't.

Just so we're all clear (I know I'm not) - 90 MJ with 93 XJ electronics, still has 90 MJ longblock, or did you swap the 93 XJ longblock? I forget how the late model intake lines up with the ports on the RENIX cylinder head. IIRC it will line up fine on the 93 cylinder head though...

You are also looking at some sheetmetal work on the firewall to make the newer interior parts line up well with it, but from what I've seen on various build threads it's not too too bad.
Click to expand...

The MJ has the 93 XJ's longblock and wiring, the MJ is for all intents and purposes a 1993.

To make this question simpler.

Could I put a '93 engine from a 4.0/aw4/np231 into a '99 xj with 4.0/aw4/np231. Just need to know any differences in the blocks/heads/crank etc.
 
Yeah, it'll be fine. You will need to swap intake manifolds, a few accessories, and cut off that funky boss on the timing cover by the timing indicators (around 2 oclock at the harmonic balancer looking from the front) to clear the serp belt. You'll also need a 1/8 NPT plug (or just leave the sender in, not wired to anything) to plug the gauge sending unit port in the cylinder head on the driver rear side.
 
Different flex plate?
 
Tyj99xj said:
Will the 99 head bolt up to the 93 block no problem?
Click to expand...
Should, but don't think you would need to change it either way. You can if you want, of course.

Ecomike said:
Different flex plate?
Click to expand...
same flex plate. 91 through 01 use exactly the same one, or rather, 91 through ?? used a different one, but the later design is compatible and is actually a redesign of the same thing, if you go to a dealer and order an early 90s one they will give you a late 90s one because they don't even carry the early 90s ones anymore.
 
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