I need to your guys' help. I have a 91 cherokee with the 4.0l. Unfortunantly it was rear ended so now it has a salved title. I have come across a 99 that needs a new motor for a good price. Would the 91s' motor bolt right up in the 99? Thanks in advance

 

I see this was posted a couple months back, but for what it's worth there were a few differences between the 4.0s in those two years. Big thing being the 99 would have had the OBDII diagnostics, both engines had different intake manifolds, power steering setups, and ignition systems.

So while the older engine might "Bolt" right in, it won't work right in the newer Jeep. Sure, there's probably ways to make it work, but IMO the effort wouldn't be worth it.