The 6 cylinder YJ up to 91 was carbeurated, 4.2 liter. After 91, I think all the engines (even the I-6s) had fuel injection(4.0 liter). I'm pretty sure that all of the 4 cylinder models have fuel injection, even before 91.
I'm not knocking the post-1990 (4.0 liter) jeeps, but I've got a 1985 CJ-7 and 1990 Wrangler, both with the 258 I-6 and I would definitely recommend this engine setup. Any maintenance (other than perhaps the AC unit) is easily done with a set of normal tools, and parts are reasonably priced (replaced a water pump on the '85 yesterday for $30 from Autozone). The 1990 has 130,000 miles and it burns less than 1/2 quart of oil between changes (never been rebuilt or anything). These engines do have a pseudo-computer, but it is quite simple compared to what I understand operates the fuel-injection unit in the 1991-and-up 4.0 liter. In fairness though, that 4.0 does have the advantage in both horsepower and fuel economy, so it's your call. Hope this helps!
Currently an '86 CJ-7 and a '77 CJ-7 Golden Eagle---#4 and 5 following a '01 Sahara, '90 Sahara, and '85 CJ-7....
No offense to the previous post, but I would hardly recommend NOT getting one of the carburated models - especially if your considering fuel economy and horsepower. The I6 4.2 has about the same horsepowerrating as the four banger - and it also sucks gas like it's going out of fashion. The post 90 4.0 are much more modern and refined engines that should last you much longer on average.
Everyone who has a post 91 model says the 4.2 sucks, but those of us with the 4.2 like it. Easy to work on, and with minimal expense you can have it well over 200horse. I say minimal, yet I haven't done it yet myself... but slowly you can add stuff to make it a great engine. The head swap is 200 or so will add 40hp, headers will add more, a new carb or carb mod more, and a head port even more... goto engine forum and read section on "what will a shade tree mech do on 258" ... basic question is what can you do for a grand. Answer, alot.
Plus the old american rumble underneath you just can't be replaced.
89 YJ 4.2L
3" body lift
2" shackle lift
32" tires on 15X10's
soon to be JKB2 mod
I had a 4.2 and swapped in a 4.0. Didn't like the 4.2 because it never ran well. I had trouble with the carb and vacuum lines and you can't get a lot of RPM's out of them. The 4.0 just runs, no matter what.
I have a 87 4.2L I6, and it has been nothing but trouble since I got it. Its great that its easy to work on, but I don't like having to work on it every week. I get about 7 MPG, but I think most people get more like 10 or 12. Good luck with your jeep buying!
It really depends what kind of mechanic you are/want to be. I have learned a ton from my 4.2, because you can work on it easily, and there isn't any real computer to screw up. I have cut half the wires out of my wiring harness, because with the new carb they weren't doing anything. Once you get a new carb to replace that old carter POS your set. Just to confirm 87-90 I6s were carburated, 91-95 I6 were EFI (Multiport Fuel Injected). I'm not sure about the 4s, but I think 87-90 I4s were Throttle body injection (TBI) and 91-95 4s were EFI think. The 87 has a weaker trasfer case than the later models, and in 94 they switched to an external slave cylinder. have fun.