my motor is dying quickly in my 96 xj, my FIL has a 1990MJ 4.0 with 122000 that he said i can have, would reaaly be great if i could use this engine, money is kinda tite rite now and this would be a huge blessing, i am pretty confident i can do the removal and reinstall myself, with maybe a couple extra hands for the critical moments. just need to know if this will work. what if anything will i have to swap over, i was thinking while i have it out putting some cheap exhaustheader on it, they are more then likey cracked somewhere, like so many others. i have been searching but canot find my exact situation, any links to this kinda stuff would be great too thanks guys!!

Its a Renix motor in the MJ, a non-Renix in the 96.

You can put a 96 in a 90 and earlier, not sure about the other way around.

And depending on how clean that MJ is, it may be worth good money by itself.

the MJ is also a manual dunno if that changes anything on the bolt pattern?

Bolt pattern? For the trans bellhousing? No, its the same. But other things are different.

Does the MJ run? Whats wrong with the XJ?

its dying noises and such i am putting a new to me in thats def set in stone just wondering about this swap. and yes the mj motor runs its out of the mj right now though. what other things are diff?

also tossed around the idea of turning this xj into a manual cause i could use his tranny too, but seems like a lot of work and this is a DD so i gotta get it up and running soon. i dont mean to be annoying with wat seem like stupid questions to u so if there is any links u know of ill go there too, i have been searching

Well, first off your XJ is OBD, the MJ is Renix. Compmetely different operating system.

Then the all the little things. For example the manual throttle position sensor vs the auto one. Not sure if the are the same for the Renix auto vs the OBD auto, so not sure if you can use your original.

Seems like the better idea would be to find one closer to your year.

Easy to do. No big deal on the fueling systems. Keep yours.

Use your dizzy, flexplate, sensors and manifolds. Use an intake/exhaust gasket for the later model engine. Any questions, post them up or PM me. I've done a coupla Renix/HO swaps. Think of it as a long-block swap and it's easy.

ok im concerned now about the 2 different responses i am getting, if you have done an actual renix motor into a newer model then i would definately love your input and help, wat is a dizzy? so i need a manifold gasket like for my 96? it will bolt right up though at least right? what is ur take on the throttle sensor thing? does anything need to be modded or fabbed up in order for it to fit? thank u so much bro!!

Dizzy is distributor. It all bolts up. No fab work. Use your intake, sensors and throttle body along with the flexplate etc as outlined before.

I didn't mind my Renix, but I'm a spoiled brat and wouldn't give up my OBDII.

Heepin won't have to give up his OBD either.

I suppose not, but that's alot of crossing over years to get the correct sensors where needed. I remember my 95 had one type of coolant sensor, my late 96 (with a factory 97 motor) has a different sensor then an early production obdII 96, and my renix didn't even have one. I know its a poor example, I just get tired of trying to match stuff up sometimes I suppose.

Again, I suppose if you take it in the light as mentioned, as a long block swap, wouldn't be too awful of a headache.

Done 3 of them with no issues. Longblock is the best way to approach it. No worries.