The '87-'90 engines got a bad rap due to the fuel-injection system that was used and a head design that didn't flow as well as the later years. The big worry isn't really the engine itself but the sensors and injectors. The iac (idle air control) and TpS (throttle position sensor) are problematic and can die with some regularity. Finding good replacements from a parts store is rough, and they aren't cheap The fuel injectors are known to leak at higher mileages, which is where the reputation for fires comes from. replace the injectors with Ford mustang parts.
The '91 and '92 mJs use the 4.0 h.O. engine we all know and love, and the sensors and injectors swap back and forth with the other Jeeps of those years. The problem is the production numbers just weren't there in the last two years of the comanche run, and not only are they harder to find but people think they command a 300 percent markup because it's "rare."
No matter what year mJ you're looking at, if it's a stick, make sure the clutch master cylinder isn't leaking inside the firewall into the fuse block because that can lead to costly and/or time-consuming electrical repairs.
We're sure we're going to get a ton of hate mail for this one: the '96-'98 ZJ with the 4.0l is another Jeep that should go the distance. notice we didn't say anything about 93-'95 models because we still think there are too many electrical gremlins in those to make them a good buy. nor did we mention the V-8 models. We've got nothing against the V-8 engine, and in fact, we prefer the ZJ with the V-8. We just don't think the 5.2l or 5.9l, in general, is a 200,000-mile engine.
Also, the ZJ got the aW4 behind the inlinesix, which is one of the few automatic, factory, Jeep-offered transmissions we'd even think about running.
LIke its 200K brethren, the XJ, look for cracks and signs of wear in the unibody at the suspension mounting points and avoid rust in the unibody like the plague.
The '91-'95 4.0l Wrangler is another good vehicle if you're trying to save a buck. yeah, we listed the yJ already, but the years of the six-cylinder are different enough that they don't really fit. get a '91-'95 yJ with the aX-15 manual transmission and np231, and you won't regret it.
Unlike the four-cylinder, where the automatic transmission makes it almost undriveable, the automatic in the six-cylinder is driveable. With no Overdrive, the revolutions needed to run it down the freeway will cut the engine's life way down, not to mention the transmission itself not making it to 200K for one reason or another. Whatever the case, avoid the automatic transmission if longevity is the goal.
Like the four-cylinders, look for rust and that recall on the gas tank, as well as any vacuum problems that might be lurking. as with all six-cylinder engines in Jeeps, valve-cover gaskets and leaking rear main seals are a virtual given at more than 100,000 miles, but in no way should that be a deal breaker.
The big reason the '91-'01 XJs with six cylinders made it up to no. 2 on the list- ahead of the yJ Wrangler-is because less of them have been beat on their whole lives. The original yJ owner was likely an outdoorsman who used the Jeep to get to remote wilderness areas or for cruising the beach- either one takes its toll. The original XJ owner was likely using it to get groceries, drive it to work every day, or pick the kids up after soccer practice. Whatever the case, we find a lot more high-mileage XJs in good to great condition than we do the yJs of that period.
The other nice thing about this XJ is whatever transmission you optioned behind your 4.0l, it was a decent one. The aX-15 and nV3550 can go to 200,000 miles without abuse and regular oil changes, as can the aW4 automatic.