Putting a newer model 4.0 into a older 4.0 Jeep

tomasmagus

New Member
Joined
Mar 2, 2007
Location
Greenville, NC
I have a 99 Jeep Wrangler 4.0 engine and I am wanting to put it into a 90 Jeep Cherokee which has a older type of 4.0. Has anyone done this before and if so is it possible? Is it a simple switch or is there something different about these two different 4.0 model engines?
 
About the only thing I can think of is that you'll need the computer, too: OBD1 vs. OBD2 You may want to check at jeepsunlimited.com or some other jeep-specific forum, too.
 
I believe it is a little bit more complicated that just swapping computers. I know enough to know it is not simple, but I don't know enough to tell you exactly what needs to be done. The fuel injection system is completely different. The exhaust/intake manifolds are different. The ABS systems are different, so you may run into issues with the computer. Thats about the extent of my knowledge. If you have a donor vehicle, it can be done.
 
The 90 cherokee is not OBD I, it is a renix controlled engine.

To do the swap you need to swap pretty much everything. Fuel Pump, Computer, Wiring Harness, all the sensors, and the entire engine assembly. It is a completely different setup. The good thing is, that even though you are swapping in an obdII engine, you dont have to worry with an emissions inspection since it is going into a 90. However, the ECU system on the OBDII, is more complex than the 91-95 OBDI system.

So pretty much You will need to graft everything from the 99 engine harness, computer, engine, accessories, fuel pump, into the 90. It can be done, but its definitely not one of the easier things to do. The hardest part is the harness/computer setup, and mating it with older harness.

The easiest way to do the swap, is with a complete donor vehicle, and a really accurate and complete wiring diagram from both vehicles, something better than whats in the back of a haynes/chilton manual.
 
the biggest concern is the security built into the 1999 jeep

Does the 99 have a grey or black key? if its grey your going to have some trouble and will need a DRB (factory scan tool) to get it to run, you'll also need the skim card and matching ECM

If its black then it has no embedded chip and your good to go
 
no it doesn't have the transponder key, just a normal one. I need to rebuild this engine anyway before I put it in the cherokee, so you think it's not feasible to do this? I didn't think that switching out the block would be so hard. I knew that I would prob have to get a new manifold and a new exhaust but the cherokee needed a new one anyways. So you think that the old cherokee computer would not run it right cause it's a newer block?
 
The blocks are prolly very very similar. There might be a couple of extra holes for knock sensors and the coil mounting holes are different but all 4.0 blocks are basically the same
 
All he really needs is just the block, not everything. He might want the head as well, but he is going to reuse all the other cherokee parts he can. We want to keep all the other cherokee stuff the same just pretty much the long block to be switched out.
 
no no no the block is not the same. different motor mounts, all the accessory mountings locations are not the same. such as a/c top right on the 90 lower left on the 99
Oil filter mounting not the same.
 
First hand experience here...

Just swap the long block into the 90. Swap the 90 intake, exhaust and front accesory drive parts onto the late model block and head. Swap your distributor and motor mount brackets as well.

I just finished doing this on my bro-in-laws 90 XJ.

You will need to run the temp sending unit into the thermostat housing. The 90 has the port for this on the drivers rear of the cyl head. The 99 will not. Drill and tap an 1/8" hole in the t stat housing and screw the sender into it. Aside from that it is a bolt in swap.

You will end up with a 99 4.0 with 90 XJ Renix injection installed onto it.
 
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