Can I put an 2003 TJ 4.0 into my 1989 MJ?

[JL]

I can get a 2003 TJ 4.0 with everything under the hood, wiring, computer, etc. Will this work in my 1989 MJ with a 4.2? Will the transmission mount right to it? What else would I need to get? Is it worth it or would it be better to just replace with an XJ motor? The TJ motor runs great only has 36,000 miles on it and will only cost me $600.00. I can find 86 thru 89 4.2 motors with less than 100k for the same and less.

 

Thanks in advance for any help!

 

[Eagle]

An 89 MJ doesn't have a 4.2, unless a previous owner bastadized it. It should have a 4.0L, but with the earlier AMC/Bendix/Renault (RENIX) injection/ignition system. Physically, the 4.0L block from a 2003 Wrangler is the same. The computer and injection system is all different, so to do the swap you should have all that stuff from the donor vehicle. The transmission from the 89 should mate up with the newer engine okay, but there might be a difference in the pilot bearing (which wouldn't be an issue if you're using an automatic transmission).

[JeepcoMJ]

agreed.

 

if you have a 4.2 in your comanche, it's been f*d with.

 

...you can put the newer 4.0 in, no big deal. you will either need to adapt it to the renix injection (probably the hardest part of it, and a waste of time IMHO), or you can pull the harness from the TJ as well and use it. you would need it's interior and engine bay harness, and you will have to do some rewiring either way.

[JL]

Had a couple of people tell me it was a 4.2 not a 4.0. It is the origianl engine so it must be the 4.0. I bought the truck from 1st owner. It has 147,000 miles on it, does not smoke at all, has a hesitation when starting and runs rough at start up but then idels fine with a slight taping every 10 to 15 minutes. Cursies at 70 mph and has plenty of power when you hit the gas. It's when it sits that the tapping starts. It does leak oil also. Firgured it would be good to replace it when I got the chance. It is an auto and has a power and comfort switch on the dash. I'm guessing it is the same as a an overdrive.

 

So it can be done but a lot of rewiring will need to take place. I guess it would probly be easier and cheaper to look for a good enigne from 86 thru 89 and just swap it.

 

Thanks for the help

[Pete M]

I'm not convinced that your engine is bad. How loud is the tapping? It could just be a loose lifter. Tapping/ticking noises are fairly common in the 4.0L.

 

And the warm up hesitation could be a simple fix.

[JeepcoMJ]

no, 87 through 89

 

86 was not a 4.0

 

 

and if you got the TJ engine, you could get a high output wiring harness from a cherokee and just replace yours with that, no problem

 

just making the TJ harness work would be a b*@$£

[JL]

The tapping is not loud and does not happen all of the time. The start up is the worst problem to me and the oil leaks.

[Eagle]

It is an auto and has a power and comfort switch on the dash. I'm guessing it is the same as a an overdrive.

Bad guess. :redX:

 

The AW4 is an overdrive tranny, and one of the selector positions covers overdrive. (On the floor shifts it's the 'D' selection with a circle around it -- I don't know what it's marked on the column shifts.) The power-comfort switch basically just changes the shift points. The power setting is easier on the tranny and is the way they came hard-wired after 1990, when Jeep eliminated the switch.

 

To lock out overdrive, move the selector lever to the '3' position.

[fiscus]

An 87 MJ should have a 4.0L & AW4 transmission if it is automatic, if it is standard then it has the BA10 Peugot tranny (& you'll need a custom pilot bushing if it's a 5-speed to mate it to a HO motor).

 

This may be of some help to answer your original question:

http://www.terrainstompers.com/forum/viewtopic.php?t=14

:cheers:

[89MJComanche]

Dude I think that your MJ is a ugly huge hunk of junk with a blown up motor. You should just sell it to me and go buy a Ford Ranger instead.

 

 

:cheers:

 

Nice Rust Free 87 MJ

[sinnaevd]

That Tj engine will get better mileage because it should be distributorless.

 

600 is a heck of a deal.

 

But as said before, your engine has the common 4.0 problems, they are more annoying than anything.

 

The swaps have been done many times before, and are well worth it in my opinion.

 

as far as engine swaps go, the hardest part will be swapping over all the electronics. But in the end, you will have a nicer MJ in my opinion.