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Jeep engine compatability

XJ[4x4]77

NAXJA Forum User
Location
Portland, OR
okay so i blew my motor up the other day out of my 1991 4.0 high output, i broke 3 connecting rods and i just got the motor out yesterday and i have the option to buy a 1997 4.0 high output but i do not know if it is compatible? does anyone know which motors are compatible with which years and if the electronics and computer systems will be the same? any help greatly appreciated!
 
Any 91+ motor can be made to work. You need to keep all of your current parts that communicate with the ECM, so that means sensors, injectors, fuel rail, distributor, etc. The power steering and tensioner bracket on the 97 is different and uses a different power steering pump. The exhaust ports will be a little different but it's not a show stopper especially if you take the opportunity to upgrade to aftermarket headers. Pretty straightforward really.
 
so there wont be any interference with going from OBD1 to OBD2? about the injectors, would i have to use the leaky steel ones that came on my 91 or could i re wire my injector harness to adapt to the newer 97 style injectors and rails? will i have to re use all my sensors off of my 91 (o2, coolant temp, oil pressure etc.) or will the new motor be plug and play to my existing wiring harness?
 
You'll want to swap over most of the sensors, what you listed:
* oil pressure sender - I'd bet either one will work fine, but it's pretty easy to swap.
* coolant temp - this changed around a lot over the years, depending on which went where and sent signals to what. Swap these over.
* O2 sensors - these are on the manifolds, so just use your old ones + your old manifolds, unless you swap manifolds too in which case use your old sensor.
* injectors - not sure but lots of people upgrade these, so I think anything with the right plugs and diameters should work.
* CPS - on the bellhousing, talks to ECU, keep your old one
* distributor electronics - keep your old stuff
* ignition - I think 91 and 97 have the same stuff but keep your old one

Your accessories are going to be different, different brackets, etc, so keep your old ones.

On the new motor - might be a great time to do a rear main seal, front main seal, timing chain if required, and pan gasket, plus a harmonic balancer if it looks like it might be going bad. Far easier to do with it on the engine stand than it is when it's installed.
 
so there wont be any interference with going from OBD1 to OBD2?
not if you use your OBDI electronics like I said in the first post. the fittings are the same, so just remove the sensors from your existing engine and install them in the donor. if you try to use 97 sensors you need a 97 computer and that means rewiring. OR YOU CAN JUST SWAP SENSORS and be done with it. The only thing that wont switch over is the gauge sender on the back of the head, so you will need to move it somewhere else. I drilled and tapped a hole in the flat spot of the thermostat housing and it works well.

about the injectors, would i have to use the leaky steel ones that came on my 91 or could i re wire my injector harness to adapt to the newer 97 style injectors and rails?
the flow rates are different so the newer injectors won't work. you can get new injectors if you want, I bought a set from http://www.fiveomotorsport.com/Injector_SetsJEEP.asp when I did my swap. the fuel return plumbing also changed so you need to keep the 91 unless you plan to rebuild the fuel delivery system
 
Injectors, just by some Ford (Bosch) orange-top 19 lb injectors, about $30 at a salvage yard for a set, were used in 3.8 L and up engines up to and including the E350 vans.
 
well i ended up buying a 1996 cherokee from a friend of mine, it was a girls and she stuffed it in a ditch and when she did it ripped one of the tranny oil cooler lines off and pissed all the ATF on the ground. She kept trying to reverse and forward out of the ditch and blew the tranny up. The motor is cherry though and it even has a 231 t case and ABS for the bigger u-joints. The body is 85% straight with great interior and only like 80000 miles on it! got it from my buddy for $500 :) now to start ripping the motor out!
 
So just to make sure, can any 91+ swap into a 2000 no problem?

I am only talking about the long block, no intake and exhaust. They will all stay with the truck.
 
2000+ introduces additional problems and should be avoided. The ignition changed from distributor to coil rail and the exhaust ports are pretty different. Also those heads have a problems cracking so I wouldn't want one anyway.
 
They changed the connectors on all the sensors in late 96, so even though they have the same amount of wires to each sensor, it won't be plug and play. Either reuse the 91 sensors or chop off the 91 connectors and solder the 97 connectors in and use the 97 sensors. The coolant sensor port that is in the back of the head on your 91 is not on the 97 head, so you will lose the dash gauge, but the pcm will still get its data from the temp sensor in the t-stat housing.
 
so i got the jeep home and did a compression test having 155-160 psi in all 6 cylinders and then started it up and it ran great! looks like it has a brand new waterpump, plug wires, cap and rotor etc. and it actually turns out its a 96 not a 97 like i thought. is 96 still OBD2?
 
It doesn't matter OBDI or OBDII, what matters is the data the ECU expects to see from the sensors. There were one or two changes every couple of years so you need to USE SENSORS THAT MATCH YOUR ECU that's all
i understand that thank you. just a simple question.
 
It doesn't matter OBDI or OBDII, what matters is the data the ECU expects to see from the sensors. There were one or two changes every couple of years so you need to USE SENSORS THAT MATCH YOUR ECU that's all


So, you are saying that if I wanted to replace the tired motor in my 95 beater with the motor in my totaled 97 i just need to swap the computer or the whole wrining harness?
 
Not to thread jack, but while we are talking comparability. Are there any differences between the sensors of a 97 & 98? It looks like I'm swapping the motor from my 98 parts jeep sooner than I planned. Can I just swap the motor with most of the sensors & electronics still attached to the motor?
 
So, you are saying that if I wanted to replace the tired motor in my 95 beater with the motor in my totaled 97 i just need to swap the computer or the whole wrining harness?

are you trolling me? the computer talks to the sensors/injectors/ignition and it all need to be the same era. if you want to keep using your 95 computer and wiring harness, then reuse the 95 sensors when you install the 97 engine. if you want to use the 97 sensors for some perverted reason then you will probably need to swap the computer and the harness from your 97 into the 95. that includes the interior wiring, fuse panel, fuel pump, ...

seems pretty simple choice to me, disconnect parts from existing engine, install into donor engine, done. that is what I did when I swapped a 99 engine into my 91 and was done quickly
 
Not to thread jack, but while we are talking comparability. Are there any differences between the sensors of a 97 & 98? It looks like I'm swapping the motor from my 98 parts jeep sooner than I planned. Can I just swap the motor with most of the sensors & electronics still attached to the motor?

go to rockauto, open a tab for a 97 XJ and another tab for a 98 XJ. compare the part numbers for the sensors, injectors, and ignition parts
 
are you trolling me? the computer talks to the sensors/injectors/ignition and it all need to be the same era. if you want to keep using your 95 computer and wiring harness, then reuse the 95 sensors when you install the 97 engine. if you want to use the 97 sensors for some perverted reason then you will probably need to swap the computer and the harness from your 97 into the 95. that includes the interior wiring, fuse panel, fuel pump, ...

seems pretty simple choice to me, disconnect parts from existing engine, install into donor engine, done. that is what I did when I swapped a 99 engine into my 91 and was done quickly
I was confused how you had an earlier post worded. NO I wasn't trolling, I wrecked my 97 and now I have a 95 with 248k on it and Really I'd rather have obd2 than obd1 if the motor on the 95 were to go bad.. I am a tard when it comes to things like this. But it looks to be a PITA to do the swap so I'll just swap the motor! :D
 
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