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Motor swap questions and help


NAXJA Member
NAXJA Member
Warsaw, IN
I am currently in the process of building a 1990 MJ for my oldest son. We have decided to do a full 2000 xj swap on it but have now found out the motor we put in it is no good so it's time for another motor swap.

I ended up picking up a 97 xj that was running to use the motor out of. I know that 97 was kind of an odd all year for the xj. With the wiring and motor we currently have in which is a 2000 with the precats, what would be the best and easiest swap to perform? I thought about just using the block from the 97 and using the sensors and everything from the 2000 but that would end up with having the exhaust ports not matching up and still being stuck with precats. Other option would be to swap the entire motor and engine wiring harness and ecu over from the 97. This way I wouldn't have any problems with the exhaust ports or deal with precats.

Does anybody know if there were any changes in the aw4 trans from 97-2000 that would prevent me from just swapping the motors over instead of complete drivetrain?

Or if anybody has any other helpful insight on best way to do this swap.

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Everything AW-4 is here >> https://www.naxja.org/forum/showthread.php?t=1053970.

I have 2000 with 0331 head and 48 state emissions and a 1998. If you have the parts, I would prefer a 1997-1999 set-up.

1996 was the one-year-only oddball, 97 has a few quirks, but is basically the same as 98-01
Does anybody know if there were any changes in the aw4 trans from 97-2000 that would prevent me from just swapping the motors over instead of complete drivetrain?

Tim already posted the biblical AW4 thread. 98 was a changeover year for the AW4 when the rear output speed sensor changed and a front input sensor was added. Best to match the AW4 with the year of the harness and trans computer.
@Jeepguy91, thanks for posting this thread!

I have a leaking rear freeze plug and an engine that can't seem to get much better than 12-13mpg no matter what I try (new exhaust, regeared to match my 31" tires, etc).

I'm thinking about dropping in a 4.6l stroker, but I'm concerned about how many other items I'll have to replace at the same time.

Does anyone have a good sense of what I should swap out as well as what I'll probably need to fix when I pull the old 4.0 and put in the 4.6?
My take, and I own a 2000 and a 98XJ. I would swap in the '97 motor and keep the 2001 trans. I would use the intake manifold from the 2000. The main issues in this swap will be the rail coil and the exhaust manifold vs header. Or, the exhaust ports are different for the earlier heads vs the square port exhausts on the 2000+ heads. Actually 99WJ + heads.
So, what to do. First, I'd look into the Viper coil swap to replace the rail coil. I am having some issues with my swap on this. The hard portion of the AC rubber line is in the way. Might be due to an aftermarket part. I do plan to put it on the head. There is a threaded hole by the oil dipstick tube and an undrilled boss. On a '95 head both are drilled. Same spacing as the Viper coil.
The exhaust port difference can be fixed with an aftermarket header for a 2000-up Wrangler. Sometimes they are listed for an XJ. Usually, not. I have one on my 2000 XJ. I have not swapped the '99 head yet. Probably late summer. I am having Chevy Valves put in them. Other mods too.

Edit: Also, a 1990 is a RENIX. I don't know if and when the contours of the HVAC box changed. The 2000 HVAC has an electronic controlled blend door. I do see the part listed on Rock Auto for '97 and up. I thought that up to '99, its a wire/cable actuated blend door. I haven't crossed that yet with my '88 Comanche.
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