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Old 02-20-2012, 12:44 PM   #1
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92 wrangler 2.5L rebuild suggestions

I am about to purchase a 1992 wrangler with a bad 2.5L 4 cylinder engine. The guy said the oil pump went out.
Since everyone says the 4 cylinder is weak on highway driving, does anyone have any suggestions on possible improvements to make while I am getting this engine rebuilt?
Engine bore, head modifications, cam?

Thanks in advance for the info. My daughter is turning 16 and she's wanted a jeep for years. The girl makes straight A's and she stays out of trouble. I would like to do this for her.

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Old 02-20-2012, 01:45 PM   #2
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How much highway driving will your 16 year old be doing? These things are notorious for poor MPGs, with gas headed towards $4 everywhere. The 2.5 is never going to be a performer, no matter what you do. I have one and have had 3.......just not gonna happen.

Vehicle is high centered, as well, cannot be driven like a normal car. Just stuff to consider.

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Old 02-20-2012, 01:52 PM   #3
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You May be better off buying a good used 2.5 and then doing the mods, seams like a lot of folks pull good engines the go back bigger.

Most all engines run stronger with an RV low RPM Cam, a light head porting, Header larger and high flow exhaust, larger TB and free flowing intake. There's not much gain in over size bore, other than to clean up the cylinders, just can't bore them bigger and get very many more cc. Now if you could stroke it, there's where some power can be found.
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Old 02-20-2012, 06:53 PM   #4
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No matter what you do to it. that Jeep wont go over 70 mph. Which might be a good thing for a 16 yr old.
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Old 02-20-2012, 07:56 PM   #5
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Dlra: if she will be keeping stock sized tires, it should be a nice ride for her. My two 2.5's on stock tires averaged 21mpg and performed fine up to about 70mph, above which they seemed overrevved and fuel economy tanked. If I were rebuilding mine, I would look into an RV cam as suggested, which tend to boost low-rpm torque and slightly increase fuel economy. I would also consider the 4.0 throttle body upgrade (and port-match the intake to the TB), and the Ford 19# injector upgrade. Most people who trade their mechanical cooling fan for an electric fan claim a slight bump in power or economy, or both. You can search for 2.5 power upgrades on the forum to see various opinions on the results of some or all of these mods, but the concensus is that they can be noticable but not dramatic.

Honestly, though, if it will be rolling on stock or near-stock rubber, in my opinion it will perform adequately and reasonably economically for what it is whether you upgrade or not.
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Old 02-20-2012, 11:07 PM   #6
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Quote:
Originally Posted by VeroJoe View Post
No matter what you do to it. that Jeep wont go over 70 mph. Which might be a good thing for a 16 yr old.
Once again.

FALSE.

This is an incredibly poor accusation towards 4 cylinder Jeeps.

Keep in mind i'm geared to 3.55 in the rear and on 29" tires, yet I can do 65mph easily. 70 if I push it a bit, 80+ if I open it up. Going up 4% grades I can still do 65mph.

How is that possible, if the 4 cylinder Jeep is "weak, underpowered, crap" etc? It's a pathetic excuse to convince someone that they HAVE to buy a 6 cylinder Jeep. Especially if it's for a first time driver. You don't NEED a 6 cylinder engine. They're nice to have for the higher HP and torque output, but they're not required. Geared right and the 2.5L will sing all day and night on the highways. Even geared badly it does fine. MPG is the same between the 2, they both offroad the same, and they both have the same problems.

The YJ AMC150 can also be modded from stock. 87-90 used a TBI system, which you can still gain 25hp+ out of (realistically it's 20hp), and the MPFI 91-95 models you can see as much as 45hp+ (realistically it's about 35hp). 10hp would make a big difference.

STOP with all of these false accusations. When you learn how to drive the 4 cylinder how it was designed to be driven, it does VERY well, around town or on the highway. It's not over-revving it if you want to run it at 3500rpm. It can be revved to 5200rpm before it redlines, max hp output is at 4200rpm. It was designed to run at these high RPM's.
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Old 02-20-2012, 11:23 PM   #7
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Quote:
Originally Posted by Xpress

Once again.

FALSE.

This is an incredibly poor accusation towards 4 cylinder Jeeps.

Keep in mind i'm geared to 3.55 in the rear and on 29" tires, yet I can do 65mph easily. 70 if I push it a bit, 80+ if I open it up. Going up 4% grades I can still do 65mph.

How is that possible, if the 4 cylinder Jeep is "weak, underpowered, crap" etc? It's a pathetic excuse to convince someone that they HAVE to buy a 6 cylinder Jeep. Especially if it's for a first time driver. You don't NEED a 6 cylinder engine. They're nice to have for the higher HP and torque output, but they're not required. Geared right and the 2.5L will sing all day and night on the highways. Even geared badly it does fine. MPG is the same between the 2, they both offroad the same, and they both have the same problems.

The YJ AMC150 can also be modded from stock. 87-90 used a TBI system, which you can still gain 25hp+ out of (realistically it's 20hp), and the MPFI 91-95 models you can see as much as 45hp+ (realistically it's about 35hp). 10hp would make a big difference.

STOP with all of these false accusations. When you learn how to drive the 4 cylinder how it was designed to be driven, it does VERY well, around town or on the highway. It's not over-revving it if you want to run it at 3500rpm. It can be revved to 5200rpm before it redlines, max hp output is at 4200rpm. It was designed to run at these high RPM's.
Win love my 2.5 she's strong as heck!
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Old 02-20-2012, 11:38 PM   #8
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Quote:
Originally Posted by SandyMushYJ View Post
Dlra: if she will be keeping stock sized tires, it should be a nice ride for her. My two 2.5's on stock tires averaged 21mpg and performed fine up to about 70mph, above which they seemed overrevved and fuel economy tanked. If I were rebuilding mine, I would look into an RV cam as suggested, which tend to boost low-rpm torque and slightly increase fuel economy. I would also consider the 4.0 throttle body upgrade (and port-match the intake to the TB), and the Ford 19# injector upgrade. Most people who trade their mechanical cooling fan for an electric fan claim a slight bump in power or economy, or both. You can search for 2.5 power upgrades on the forum to see various opinions on the results of some or all of these mods, but the concensus is that they can be noticable but not dramatic.

Honestly, though, if it will be rolling on stock or near-stock rubber, in my opinion it will perform adequately and reasonably economically for what it is whether you upgrade or not.


It should be a nice rig with just a very few mods, just go for it sounds like your a good Pop.
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Old 02-21-2012, 09:32 AM   #9
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I read alot of posts where people bash on the four bangers. Also have read a few where they say that a 2.5 will not go over 70 on the highway. My jeep will do alot more than 70 haha. I am a big fan of the 2.5 I have had both and will pick the 2.5 over the 4.0 any day. it's nice to see guys stick up for them when there getting bashed.
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Old 02-21-2012, 09:36 AM   #10
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There are only two problems with a 2.5. Eventually it will blow a rod out the side of the block, and they get about the same mileage as a 4.0.
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Old 02-21-2012, 09:50 AM   #11
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You hit the nail on the head everytime haha.
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Old 02-21-2012, 09:54 AM   #12
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Quote:
Originally Posted by Xpress View Post
Once again.

FALSE.

This is an incredibly poor accusation towards 4 cylinder Jeeps.

Keep in mind i'm geared to 3.55 in the rear and on 29" tires, yet I can do 65mph easily. 70 if I push it a bit, 80+ if I open it up. Going up 4% grades I can still do 65mph.

How is that possible, if the 4 cylinder Jeep is "weak, underpowered, crap" etc? It's a pathetic excuse to convince someone that they HAVE to buy a 6 cylinder Jeep. Especially if it's for a first time driver. You don't NEED a 6 cylinder engine. They're nice to have for the higher HP and torque output, but they're not required. Geared right and the 2.5L will sing all day and night on the highways. Even geared badly it does fine. MPG is the same between the 2, they both offroad the same, and they both have the same problems.

The YJ AMC150 can also be modded from stock. 87-90 used a TBI system, which you can still gain 25hp+ out of (realistically it's 20hp), and the MPFI 91-95 models you can see as much as 45hp+ (realistically it's about 35hp). 10hp would make a big difference.

STOP with all of these false accusations. When you learn how to drive the 4 cylinder how it was designed to be driven, it does VERY well, around town or on the highway. It's not over-revving it if you want to run it at 3500rpm. It can be revved to 5200rpm before it redlines, max hp output is at 4200rpm. It was designed to run at these high RPM's.
Thank you! I have a 2.5L myself and im kinda gettin sick of EVERYONE saying that the 2.5L is worthless.. its actually a very reliable engine.. and ive done little to no engine mods and with a 4in rc lift, and 33in mud terrain km2s.. i can get easily above 70 on the highway.. which actually translates to like 78mph once u account for bigger tires.. :x anyway.. idk where people come up with not being able to go over 65mph... honestly lol.
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Old 02-22-2012, 02:55 PM   #13
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I think the 4 banger is an awesome ride!! Heck I got one. For a 16 yr. old boy or girl even better!! Lets face it, @ that age your experimenting with everything and if that rig could go up to a 100mph they would be pushing 105 mph on it. I wouldnt want to see an inexperience driver going that fast on any road. So 65 mph sounds just fine for a loving dad and his loving princess.
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Old 02-22-2012, 07:01 PM   #14
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The 2.5 would be the best thing for a teenager just starting out. There really isn't a lot of maintainence cost on the tune ups and stuff. My 17 y/o has an XJ with the 4.0, and he is always spinning wheels. It aggrivates me.
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Old 02-23-2012, 07:57 AM   #15
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92 wrangler 2.5L rebuild suggestions

I really appreciate all the input. Sounds like I could get a good vehicle out of that jeep if I'm willing to put in the time. Also sounds like I better be willing to fork over some gas money since its 45 miles round trip to school where we live.

If I am able to convince her mom that her daughter would be safe in the Jeep, does anybody have any websites suggestions where I can buy an A/C system kit? It gets pretty darn hot here is South Alabama.....100F with 90% humidity.....hard to breath.

Do you folks think that my local machine shop should be able to handle this 4 banger rebuild without many issues?

Thanks again for all the input. I can see that Jeep owners are a separate breed.
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Old 02-23-2012, 09:07 AM   #16
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wish I saw your thread 4 days ago, just yanked my ac out and would have given it to you.
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Old 02-23-2012, 10:27 AM   #17
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I don't know about putting ac on a 4 cyl. I don't see a reason to put ac on a wrangler at all
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Old 02-23-2012, 10:43 AM   #18
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AC is nice when your in a drivethru.....it also makes your rig worth about 1500 more on resale
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Old 02-23-2012, 02:04 PM   #19
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AC is going to rob a lot of power, better ditch the mechanical fan now in favor of an electric fan. Something that will turn on when the AC turns on. As well as installing an
"idle up solenoid" which will rev the engine up to about 1200rpms to drive the AC compressor better.

If you have a soft top- forget it. It's not going to hold cool air inside at all. Better to remove said top and enjoy the natural AC.

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