Jeep Wrangler Forum banner

need advice on 4 cylinder

9K views 27 replies 17 participants last post by  Xpress 
#1 ·
just bought a 88 yj with 4cylinder. are all jeep 4 cyl. this weak? i have a dodge dakota farm truck with a 4 cylinder and it has a lot more power than the jeep(in 2wd). my previous jeep was a 79 cj5 that i bought new and it had a 258...wish i had it back!!!!! how much changing will i have to do to put a 6 cyl and tranny from a 90 yj in mine????? i have found a complete motor and tranny for 600. any advice is welcome.
 
#2 ·
Not all of the 4 cylinders are that bad. The fuel injected ones are much better. In 95 they vamped up the 4 cylinder is a nice one, and they used it until the later tjs. As for taking it from a 90, it shouldn't be to bad. I don't know if the mounts are the same or not. I really suggest finding a fuel injected engine. 350 small blocks are easy engines to mount, and will provide you more performance you are looking for.
 
#6 ·
i would not install the 258 in place of the 2.5. the fuel injection is a big plus on the 2.5, the carb on the 4.2 during that time is problem prone. but if you know carbs, and don't mind dealing with that, or maybe put fuel injection on the 258 then its a good engine.

the mounts on the frame are not the same, so the frame has to be modified. and i forget exactly when they started using the ax 15 exclusively, if its a manual trans it may be the peugot, and that sucks as well.
 
#8 ·
my 95 yj has the 2.5l and it moves with traffic well as said above. the only thing i find wrong is the need to downshift on highway inclines to stay at speed. 5th gear, at high speeds, seems to only be there to maintain that speed. Acceleration in 5th on the highway is minute.

towed my buddy's 2g eclipse to the shop the other day with no problems! :punk:
 
#10 ·
The best answer I can give you is this: Live with the 4 or sell it and get a 91 or newer 6cly.
 
#11 ·
If you do any sort of engine swap, go for the fuel injected 6 cylinders. They are 4.0L, easy to work on, and reliable.

The AX-15 was put in the mid 1988, and is probably one of the better wrangler transmissions. It was only in the 6 cylinder, but if you are going to use any of the AMC 6 cylinders that's your best bet.

Odds are is that you have the AX5, which is a really pretty weak tranny, so I wouldn't test it behind a 6 cylinder. You should head on over to Novak Conversions web site (Novak Jeep Conversions - Home). They have a lot of great info about putting GM engines and trannies Jeeps, and actually offer a lot of info about what came stock in YJs.
 
#13 ·
I currently own a 94 2.5 and it is pitiful. It doesn't have enough power to pull a string out of a cats rump. I have done verything to it and still no power. And the sucky thing is no matter what you do to them your still only going to get between 11-15 mpg. No matter what anyone tells ya, I am living proof. I have spent a small fortune on my 4 banger and all I got was a little quicker take off and no better MPG. These engines are a joke. The designer of these engines must have been drunk. I mean just think about it, these Jeeps weigh nothing and one would think that they would get awesome gas mileage but thats not the case. The only way that you can get incredible MPG is to buy a small diesel engine out of a Kubota tractor or something like that and mount it in your jeep. I recently seen a 93 YJ with a 3cylinder Kubota engine that had 33 HP and it got like 60 MPG and had about the same amount of get up and go. He told me that he bought the motor at a salvage yard for 250 bucks and it cost him 350 for the conversion plates and mounts, plus they fabricated it in there garage. So for less that 700 bucks he had an incredible set up and the kicker to it is, he's making his own fuel from used cooking oil from local resturants.
 
#14 ·
eky, I'm not so sure what you are talking about. The 2.5 is really a decent engine. The MPFI model was a great 4 cylinder, and they used them up until 2002. Don't get my wrong, I'd take the 242 over my 150 but I really don't mind it. The gearing in the 4 cylinder YJs is 4.11, which gives you enough power to pull you out of a lot. I guess I'm just getting defensive about my little YJ. It's no Chevy 350, but I wouldn't say that it's a terrible engine. You'd also be making a huge mistake to go with a 33hp Kubota engine.... The AMC 150 almost 4x more powerful then that kubota engine.
 
#16 ·
You can kill anything if you try hard enough, but jeepers with the 2.5 are largely very proud of the little beast. If it's so anemic, you likely have issues that need resolving. Give it a good tune up, new fluids, filters, plugs, wires, clean the injectors and TB, and maybe you'll see an improvement. That being said, if you're running huge meats on the 4 banger, it's going to take more power to turn them, 4.11s or not.
 
#17 ·
This is all true and everything you all have listed is true but I must disagree just a tad. My 2.5 is astrong very reliable engine and probably will be running long after the jeep body is gone or re-done for the 12th time. However IMO that is it's only strong suite, is it's reliability and dependability but for an everyday driver like I use mine for and an occasional weekend of outdooring it is pretty much useless for my needs. I have done just about everything that shade tree mechanic can do to improve the performance of the little engine and the only thing I got was just a tad better take off and maybe and this may be stretching it, I may have gained one more MPG. I get about 11MPG now where I was getting 10-10.5 MPG. It is very weak and in fact my neighbor made fun of me the other day when he took his Honda Big Red and about pulled me into when we hooked up bumper to bumper and before you say it yes we did both front and rear hook ups. I was so embarrassed and was even more embarassed when my other neighbor took his 1988 Suzuki Samari and drug the Big Red like it was nothing and then my Uncle used his 2000 model Chevy Tracker and did the same thing. These Jeeps are just grossly underpowered. The Samari is not half the size of my jeep and has only half the motor size that I have. The 2.5 was designed for everyday drivers like me not for "Billy Bob" the great outdoorsman but they were not designed for major 4 wheeling, mudding or crossing deep channels of water like I do in my CJ with the big six cylinder. As for the Kubota or which ever Diesel you choose I think it's win win and dont see how anyone could say otherwise. For one thing neither motor is eat up with HP but there are two huge huge differences. Low end torque and MPG and the 2.5 is not even in the same universe as the small diesel. I actually seen a Ford Ranger (recently converted over to diesel, the motor was out of a pull along lighting system, 3 cyclinder Catepillar I believe) over the weekend 2 wheel drive, 5 speed that he said he gets nearly 60 MPG and is eat up with power. Now how can a person even compare the two, is beyond me. I have a buddy that took a 91 yj with a blown motor and replaced it with a 289 out of a 66 Ford Galaxy and did all the work himself and he got the motor for free from a family member and for less than 300 bucks he had this motor in there running and he told me he gets around 30 MPG and is absolutely eat up with power and performance. He said it probably borders dangerous
 
#18 ·
I've got to say eky, I think something is wrong with the engine to be that weak. My 94 2.5 with the 5 speed has no problem accelerating swiftly, Wheeling it's way out of anything i've managed to throw at it, getting a good 13-15 miles to a gallon, spinning the tires through first gear and partly through second, chirping the tires shifting into second, and getting darn close shifting into third. I mean, I won't get 15 miles to a gallon driving it like THAT, but it's got the capability.
 
#20 ·
No I have not dont a compression check because the motor runs great and uses absolutely no oil in between oil changes and has never smoked. This isn't my frist rodeo and I have dealings with these motors in the past and they just do not have any power and they suck as far as MPG goes. Just my opinion though, don't mean to step on any toes.:banghead:
 
#21 ·
NO sore toes here, just wondering why so anemic. I have the 4.0, and while it's no race engine, it's got enough for me. I see so many 2.5 jeepers who swear by their motor, I figured it might be something with yours. Given that you've done just about everything there is to do short of a rebuild, compression loss seemed like the next thing to check.
 
#23 ·
Hahah. No sore toes here either, I just can't help but think either you're used to a much faster vehicle, or there's a problem with the engine. 2.5L TJ, and my 2.5L YJ both do very well. Hell, the TJ has put a turbo diesel in it's place once or twice. Not that that is too great of a feat, but hey.
 
#24 ·
You can forget about fuel economy pushing a brick like Wranglers. The TJ is a LITTLE better, but not much.
The minute you add any lift, lockers, off road tires, etc, it's going to get worse.
I've never gotten worse than 13mpg to a tank w/out being in 4wd, and a best of 16mpg.
The AMC 4cyl motors are awesome motors. Though they don't make as much power as the newer DOHC style engines, they offer incredible reliability.
 
#26 ·
They might not be powerful, but who drives a Jeep to make power? My 2.5 L does great in the dirt, mud, and snow when I put it in 4low which is where it really counts. It may not make as much power and speed as say a 350, but even mine with 35"s the 4.10's pull right along off-road. I'm pulling the axles this weekend and putting 4.88's and detroits in and I'm sure it'll make it even torquier off-road which is where it really counts if you think about it. We don't drive a Jeep to go 100 mph down the highway, we drive it to crawl off-road. Just my two cents.
 
#27 ·
It's true, these are weak motors and mpg isn't great but it's a JEEP and I'll take the reliability and save money until I'm ready to toss in something better - on that note, my buddy has one with 310,000 without a hiccup.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top