Engine Swap Question

[Mose705]

Hey Guys,

I've been going through the forum and have seen a lot about the 4.2 to 4.0 swap, everybody suggests going with the '91-94' 4.0 HO because of that fact that its the generation prior to 'OBDII'. My Question is why not the 'OBDII'? Other than the fact that it the emission killed the motor, what else is wrong? Is the wiring that intense? Is it the emissions? I would like to go with the '91 to '94 but its just impossible to find in my area unless i buy a jeep with it in it, and after owning 9 wranglers i just dont ever want to see one in my yard again haha not to mention that they want an arm and a leg for them.Also I found a 96 4.0 with harness and ax15 tranny for 600 OBO. If these questions were already asked I'm sorry, I am still figuring out the best way to navigate the forum.

Thanks again,

- Chad

[Draekon]

I believe the problem is with the alarm systems.  Basically you would need to find a donor OBDII wiring harness that does not have an alarm system tied into it.  If you have the VIN of the car, you should be able to call a dealership and ask if it had an alarm system.

[Mose705]

Excellent thank you very much!

[Nightpath]

I did the swap to the 4.0, wiring and all. There are less sensors with the OBD1, less wiring and you can be 100% certain of no alarm messing up the swap.

OBD2 Cherokees never had an alarm for the most part though, so if you were willing to do a bit more work then it is 100% doable.

I will add that the ODB1 matches up to the stock Eagle very nicely, even the connections on the steering column are pretty much the same.

[Amc1320]

I could be wrong but I seem to remember the alarm issue was mostly with Grand Cherokees with the 4.0

[DAVE]

I would steer clear of 1996 OBDII the first year for OBDII a lot was changed after the first year and a lot of parts pertaining to the emissions are specific for just that year and you won't find any performance chips for that year either or really hard to find

[captspillane]

I would steer clear of 1996 OBDII the first year for OBDII a lot was changed after the first year

That is probably true for most cars.

I completely disagree when we're specifically talking about Jeep Cherokees and Grand Cherokees. That is the best year to get. I generally only buy 1996 Jeep Cherokees and some early 1997 ones before the midyear changes. After mid year 1998 I avoid those engines like the plague.

It is true that parts started changing in 1997, which makes 1996 different than later OBD2. What is pretty great, however, is that the parts from the years prior are still compatible with 1996. The dash is the same, the AW4 transmission is backwards compatible, and the 4.0 itself is backwards compatible to earlier years. Since transmissions and engines from the 1990 to 1995 OBD1 era are more plentiful and consistant, I rely on that supply of used parts.

In later years they added a second catalytic converter into the header that makes it much harder to work with. They changed the bolt pattern at the same time so you can't use older heads with the new manifolds. The new heads are prone to cracking, and many of the newer engines are bad and unavailable. They added a second sensor and changed the inputs to make older AW4s unable to work in the newer Jeeps, even though the newer AW4s can still be made to work in an older Jeep.

[Nightpath]

The bad run of heads lasted 1997-1999 1/2 I think, I can't remember the casting number though. The crossover year for 1996 I've heard both good and bad about. The good is less sensors. The bad is the amount of wiring.

I think for the XJ the alarm systems were optional but for OBD2 and up, and only in the later years (found 1 in a junkyard). I forgot about the catalytic converters. Friggen headaches.

[carnuck]

The bad heads were more in the coil on plug '99 1/2 up to '03 motors. If you get one, look for the TUPY casting in the head which is the improved/replacement version. Some of the '91-95 XJs I've had ran the stupid factory key chip that sits under teh dash. The card wears out, gets corroded and then suddenly, your Jeep won't start. I fixed several by soldering jumpers across the matching contacts but that's a pain!

[carnuck]

I would steer clear of 1996 OBDII the first year for OBDII a lot was changed after the first year

That is probably true for most cars.

I completely disagree when we're specifically talking about Jeep Cherokees and Grand Cherokees. That is the best year to get. I generally only buy 1996 Jeep Cherokees and some early 1997 ones before the midyear changes. After mid year 1998 I avoid those engines like the plague.

It is true that parts started changing in 1997, which makes 1996 different than later OBD2. What is pretty great, however, is that the parts from the years prior are still compatible with 1996. The dash is the same, the AW4 transmission is backwards compatible, and the 4.0 itself is backwards compatible to earlier years. Since transmissions and engines from the 1990 to 1995 OBD1 era are more plentiful and consistant, I rely on that supply of used parts.

In later years they added a second catalytic converter into the header that makes it much harder to work with. They changed the bolt pattern at the same time so you can't use older heads with the new manifolds. The new heads are prone to cracking, and many of the newer engines are bad and unavailable. They added a second sensor and changed the inputs to make older AW4s unable to work in the newer Jeeps, even though the newer AW4s can still be made to work in an older Jeep.

The Grand Cherokee "passive" alarm with door lock triggers and chipped keys is a PITA. You can mod the older intakes to fit the newer heads and vice versa but it's labor intensive. '91 up intakes all interchange with the newer heads AFAIK. I want the newer intake (late '99 up) which should clear the brake booster fine.

The '91 to '95 XJ and Wrangler wiring and computer is easiest to hook up but you can use newer motors with a few sensors swapped and in some cases a hole drilled/threaded for the coolant sensor.

[Mose705]

thanks again for all the info guys! sadly the project is on hold until I can find a shipper (which has been awful so far ...3700$ for the car I pid 1200$ for) but she is safe and sound at my buddies place in grande prairie Alberta. currently I'm just not interested in a 60 hour drive haha

[Nightpath]

Where do you live Mose?

[Mose705]

Sorry for the late reply guys, it's been a headache trying to get the other eagle over here... I'm out in Sudbury, Ontario.. the motor I was looking at is sold but I do have a 97 Cherokee in the yard, But after reading through some of the answer here and other posts in the forum, I might just stay carbureted and hope for the best for the winter. In other news I will be getting rid of a lot of parts that (as far as I know ) won't be needing 4 of haha so if there's anything anybody is interested in getting I'll be opening a thread in the 'for sale' forum for the parts I'm parting with.

-Mose

[carnuck]

Are you talking about not going 4x4 or just not the EFI?

[Mose705]

not going EFI , not going 4x4 is not possible as far as I'm concerned