Join Date: Apr 2005
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Re: Can I swap a 2004 vintage 4.0 in my 91 YJ?
Now that I think about it more, I believe there are differences in the heads and your 91 manifolds may not fit right. Whether you can put 91 injectors in a, say, 2003 manifold, I don't know but I think there's a good chance you can.
The CPS is on the bellhousing, you didn't mention swapping that so I assumed you didn't intend to. If you want the new transmission that raises other issues.
The O2 sensor is in the exhaust system, most other sensors are in the intake manifold/throttle body assembly. I'm pretty sure you could find places for other misc. sensors, oil pressure, water temp etc.
Hmmm... it may not be as simple as I first thought! I'd recommend asking around on some other Jeep boards if no more info is forthcoming here.
I still say it can be (and most likely has been) done.