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Mark, 22 Year Factory trained technician
Category: Jeep
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Experience:  Jeep factory training........25 years in the industry.
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3.7 liter engine in 2002 Jeep Liberty, are all 3.7 liter engines

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3.7 liter engine in 2002 Jeep Liberty, are all 3.7 liter engines the same and will work in my liberty?



No not all 3.7 L are the same, there are minor internal timing gear differences and there are also set up differences for emissions and the cylinder heads are different depending on year


In the Chrysler's parts catalog there are four different complete 3.7 L engines listed


2003-2002 3.7L V-6 KJ Body (w/JTEC Controller)

2004 3.7L V-6 KJ Body (w/NGC Controller)

2006-2005 3.7L V6 All

2007 3.7L V6 All


As for cylinder heads


2004-2002 3.7L V-6 (right)

2004-2002 3.7L V-6 (left)

2006-2005 3.7L V-6 (left)

2007-2005 3.7L V-6 (right)

2007 3.7L V-6 (left)


For an 2002 you will need a 2002 or a 2003 engine to work correctly with no modifications


I hope that this helps you


Thank you



Customer: replied 8 years ago.
Ok, so what modifications would be needed to fit say a 2004 engine into my jeep? would i just have to transfer sensors over? is one year better and more reliable? my current engine a rocker came off and hit the piston, it has 140 k miles would it pay to just replace the piston and rings and cylinder head or should i replace the whole engine with a lower mileage one. How can i avoid this happening in the future? i was told it was caused by an excessive plug gap.

The 2004 engine uses a different type of engine controller. This will require that the complete engine harness and controller from the donor vehicle be used in your 02 vehicle.


There are likely some other things that may need to be considered but those are the MAJOR ones off the top of my head.


Depending on the amount of internal damage you may be better off to repair the engine you have and save yourself all the hassles.


Oh, and by the way an excessive plug gap could never cause this. If anything it might be a maintenace issue with sludge and carbon build-up.




This is a PAY SITE so if I have answered your question to your satisfaction a simple ACCEPT would go along way. Feedback and Bonuses are also welcome.

Mark, 22 Year Factory trained technician
Category: Jeep
Satisfied Customers: 11328
Experience: Jeep factory training........25 years in the industry.
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Customer: replied 8 years ago.
Just to clarify and then i will pay you, You think that even though my engine has 140,000 miles I would be better off buying a cylinder head ($600) and a piston and rings versus a complete engine with 40k miles for 1500. Do you think my engine has much life left in it at 140,000 miles? Sorry to keep on asking so much i just need an expert opinion, also how much labor is needed to replace the engine, how hard of a job is it? Im also a mechanic but have only done chevy vw and a few hondas. Thanks.



I would go with the newer engine


You will need to swap the right hand camshaft timing gear from the 2002 into the 2004 for the 2002 camshaft sensor to work


You will also need to put a 2002 crankshaft sensor into the 2004 engine


When doing the swap use the 2002 fuel rail and injectors and swap all of the electrical sensors on the top end, MAP, TPS, KNOCK (under the intake), IAT, ETC,AND Idle air control, and any other bolt in sensor


This will give your 2002 KJ a slightly different emissions profile, but ultimately it should be cleaner due to the head redesign in the 2004


You do not need to swap harnesses and controllers, just make the 2004 engine appear to be a 2002 engine to the controllers and you should be fine


Thank you



Customer: replied 8 years ago.
How many hours of work am i looking at here with no lift?



It is hard to say, not knowing what you have for tools and equipment or hands on experience, but if you are comfortable with the use of tools and working on cars then:


With the tear down of both engines, swapping parts and removal and re installation, with out a lift I would think that you could get it done with two solid days of work, the exhaust is going to be a bear to get apart lying on your back, be sure to use stands and safety devices when doing the job, please be safe



Customer: replied 8 years ago.
What about a 2005 engine?
The same applies to the 05 as the 04.
Customer: replied 8 years ago.
Great thank you so much for your help one cylinder head is already off the old engine so it should go pretty smoothly. Did the 2005's change of compression affect performance at all and are you positive that this will work with only changing sensors over. ,,, Im gonna owe you a bonus too you have really done alot of research. Thanks
Good for you, let me know how you make out as you go.


BONUSES are always welcome! Laughing

Customer: replied 8 years ago.
Did the 2005's change of compression affect performance at all and are you positive that this will work with only changing sensors over. ,,,



I suggested fixing what you have........depending on the amount of internal damage.


The other expert is the one who is suggesting making another fit. His way will break federal emmissions laws and I don't wish to be any part of that.


So, to answer your question...............the other expert will have to confirm that this will work for you because I will not.


Have a great night.

Customer: replied 8 years ago.
Sorry about that, so let me hear your opinion then, motor has 140k miles the cylinder bore suffered no damage so the motor would need one piston and one cylinder head would a piston out of a 4.7 be the same thing? How much life is left in this motor? Should i changed any other parts? like the valve springs? It would be great to fix what i have and get me on the road sooner, its no fun driving a corvette to work in traffic. Thanks in advance.
Customer: replied 8 years ago.
I never realized i was talking to two people, so who did i pay already lol?

I can only advise you the same way I would treat my own vehicle.


Granted I may have a better understanding of the overall condition of the engine just by opening it up and looking at the condition of it. Is it clean? Does it have sludge build-up? etc.


Too many times I respond to questions about people doing engine swaps involving different year vehicles and there are always stumbling blocks and hurdles you have to go through to get it to run. philosophy is fix what you have or get a direct reman replacement.





As for butting in just look at the thread and you will see who answered first and whose answers contain real information and not just fluff


When you buy a reman motor from a high quality manufacturer, like ATK, they give you instructions in the crate on how to verify the new engine compared to your original and how to make the newer engine work in an older Jeep, and those where what I passed along to you


I have done this myself in the past


A high quality reman while being more costly then a junk yard motor normally will carry a very good warranty, Chrysler has a 3 year 100,000 mile warranty on theirs, and most of the other major manufactures have the same or better


2003-2002 3.7L V-6 KJ Body (w/JTEC Controller)


List Price:5,440.00 USD


I know that you can get this from an outside vendor for much less money


Good luck with your Jeep





Customer: replied 8 years ago.
Sounds like battle of the techs here. Thanks for all your help it is greatly appreciated. I just purchased an engine with a one year warranty and 57k miles locally for 1300.
Good for you!

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