What year did the 4.0 suck?

[Leady]

I remember reading on here once that the 4.0 had a year or two when Jeep did something to it that made it not quite as good as the rest of em. I'm asking cause a friend is looking to buy a 95 and I told him I'd find out.

[Bill]

I don't think that it sucked once it was the 4.0, now the 4.2 is another issue.

[limegreentj]

all the 4.0's were good, but i think 94 or 95 was the year where they ran the best and had the most power, because they were changing emissions over.

[Leady]

yeeaaaaah that's what's up. I'm trying not to let him buy another pain in the ass he's real good at buying cars and when they break down he has no idea how to properly diagnose them. Good news then.

[tjblair]

I can't remember the year, but I thought some were more prone to warp the head.

[Mykal]

Starting in '99 I believe, they changed the emissions. The '00-'01 the head was changed and is more prone to failure.

'96 and '99 are generally the sought after years.

'99 had the highest h.p. and torque ratings out of all the production years (195 h.p/225 torque)

Stick with '91 through '99.

[justin'sbig7]

the one in my 03 is a turd.... wifes 97 xj is a strong runner though

[ridgerunner97]

My 97 has sum serious nuts compared to my cousins 99 and mine has 30k more miles on it and has led a more vicious life LOL

[limegreentj]

my 97 ran pretty good...and it had 192k on it...but ill tell ya what....i put that one from 95 in there with approximately 100k....and its got a LOT more power.

[YJBeef]

yup.....the 00-01's were the head problem ones........Justin, something must be wrong with hers then cuz my 03 runs freakin awesome compared to others Ive driven before! the one in the 95 ZJ is a dog!!!!! I think my 94 2.5 had more nuts!

[andrew2516]

'99 had the highest h.p. and torque ratings out of all the production years (195 h.p/225 torque)

Stick with '91 through '99.

99 had the same horsepower/torque as anything from late 96 through 01.

4.0L I6 EFI "Power Tech" - 177 hp @ 4750 rpm, 220 ft lb @ 4000 rpm - used 1987-1990

4.0L I6 MPI "Power Tech HO" (High Output) - 190 hp @ 4750 rpm, 220 ft lb @ 4,000 rpm - used in 91-95 and updated in 1996-2001 to 225 ft lb torque @ 3000 rpm (2000-2001 models use a distributorless ignition system)

To be honest though, I would stay away from obdII if you can just because I like the simplicity of the old system. With OBDII CEL's are more of an issue along with the possibility of California Emissions.

[limegreentj]

my tj is obdII and once you learn what all the sensors are and what they do, its not so bad...it takes a while to learn it all, but it takes a lot to learn obd1 too.

[Deadman 94 xj]

99 had the same horsepower/torque as anything from late 96 through 01.

4.0L I6 EFI "Power Tech" - 177 hp @ 4750 rpm, 220 ft lb @ 4000 rpm - used 1987-1990

4.0L I6 MPI "Power Tech HO" (High Output) - 190 hp @ 4750 rpm, 220 ft lb @ 4,000 rpm - used in 91-95 and updated in 1996-2001 to 225 ft lb torque @ 3000 rpm (2000-2001 models use a distributorless ignition system)

To be honest though, I would stay away from obdII if you can just because I like the simplicity of the old system. With OBDII CEL's are more of an issue along with the possibility of California Emissions.

^This, plus 99 had the better intake manifold IIRC. There's a big difference between my 94 and the 96 I have now.

They also changed to an aluminum piston at some point. Maybe 97?

[Deadman 94 xj]

Here's a good read:
http://www.jpmagazine.com/techarticles/engine/154_0604_jeeps_kick_ass_engine_history_4_liter/index.html

[sethman15210]

i have a 95 but in the past ive had a 93 and a 99 xj's. for power, ease of maintence, and reliability i much prefer my 95. i am also a trained jeep/chrysler dealer mechanic and i gotta say when they went obd 2 they played with a lot of systems they shoulda left alone. the only advantage for power was the 98-99 intake/ exhaust manifold. just because the intake had smoother runners and a slightly larger air volume. but that manifold can easly be adapted to a older 4.0l just keep your throttle body and fuel rail. obd 2 is fine if you want cheap unreliable power from chips and programmers, but nothing beats swapping hard parts to bigger and better.

[JeepSteeler]

My 95 snorts pretty well (with header and FIPK), seems to pack just as much if not more punch than the later model XJ's and such that I have driven here and there. My brother in law's 3.7 Liberty sees my tail lights easily.