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Discussion Starter #1
So, I own a 93 YJ with a 2.5L. It has relatively low miles (about 80k). While driving on the highway in Colorado, it can't maintain 75 without me keeping the pedal crushed to the floor and if a hill comes up, I lose all momentum and it drops to 65 at best.

The YJ is stock.

Is this normal? I know the highway performance is weak, but I am just trying to confirm if it is normally this weak, or if I have another issue. I am already considering a timing chain replacement and some other tune up items.

Note, I am not asking about how to get more horsepower. There are plenty of threads about that already. I am just trying to determine if my YJ has a mechanical problem of some sort.
 

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So, I own a 93 YJ with a 2.5L. It has relatively low miles (about 80k). While driving on the highway in Colorado, it can't maintain 75 without me keeping the pedal crushed to the floor and if a hill comes up, I lose all momentum and it drops to 65 at best.

The YJ is stock.

Is this normal? I know the highway performance is weak, but I am just trying to confirm if it is normally this weak, or if I have another issue. I am already considering a timing chain replacement and some other tune up items.

Note, I am not asking about how to get more horsepower. There are plenty of threads about that already. I am just trying to determine if my YJ has a mechanical problem of some sort.

Yeah that's pretty normal for the 2.5, it's not just the engine that is underpowered, but the gear ratio in your axles, not the best for high-speed cruising. I've owned my YJ for 10 years and have never, ever, gotten it above 75 mph, even on a flat-run lol.

A timing chain at 80K? That seems a little low, I have 210K on mine and haven't replaced the chain yet lol. But, if you have the time, resources, and tools to change it, why not? You said it's stock right? You do have some options to squeeze out more power. Upgrade to a 4.0 Throttle Body, add a 1" TB Spacer, get a high-flow K&N filter, Get a Cold Air Intake, Install an Electric Fan and free up the HP going to the stock fan pulley, etc. Like you said there's a ton of threads on that and all you're going to find is that nothing is going to get you the 6-cylinder high cruising speeds... except for a 6-cylinder lol

I don't think you have any mechanical issues though, just keep that thing in good shape, tune her up every now and then, and don't beat on it, and you'll be just like mine at 130K miles later.
 

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I can barely get up to 60 downhill I've hit 70 but that was just a big hill lol....I have 31s and im used to having fast cars so this is a slow cruiser mud machine I just feel bad for the people behind me but then again I don't care lol
 

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nicks_yj said:
I can barely get up to 60 downhill I've hit 70 but that was just a big hill lol....I have 31s and im used to having fast cars so this is a slow cruiser mud machine I just feel bad for the people behind me but then again I don't care lol
That's what I say too I don't care about the cars behind me. I think people expect a Jeep not to be that fast anyway, it's not like we're driving Lambo's in the slow lane. Yeah if your used to fast cars then the Jeep is a turtle, luckily for me my Jeep was also my first car, now everything I drive seems fast lol.
 

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Lol I drove my moms car the other day almost threw my knee out tryin to use the clutch (which isn't there ) and couldn't figure out how to put it in drive lol
 

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Discussion Starter #6
That is what I figured. I was hoping I had an issue that a tune up would fix.

I don't expect a racing machine, but I do like to cruise at speed when on the highway. I will need to drive it from Arizona to a northern state (yet to be determined) sometime in the spring. I'm not looking forward to that drive. I may tow it.

The timing chain on mine has stretched enough that you can hear it "knocking" a bit. I thought it was a piston knocking but a mechanic identified the chain as the culprit. I'm overseas right now, so I'll have him change it for me.

I have installed a cold air kit on it and I'll probably replace the distributor cap, wiring, etc soon. I do have an electric fan for it but it is still in the box. I might install it in December when I am home on leave. I doubt I will do anything more than that. Ill give it to my son as his first vehicle next year and get myself a 6 cylinder version.
 

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Ill give it to my son as his first vehicle next year and get myself a 6 cylinder version.
Good idea, kids don't need to be driving high powered toys for their first car :thumb:

They cruise just fine. If you get to a hill you're definitely going to have to drop out of 5th, but it's just an overdrive gear anyways, not made for going uphill. Hell the 3.3L V6 Highlander we have drops out of 5th going up some of the steep highway slopes, and that car is no slouch when it comes to power.
 

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That is what I figured. I was hoping I had an issue that a tune up would fix.

I don't expect a racing machine, but I do like to cruise at speed when on the highway. I will need to drive it from Arizona to a northern state (yet to be determined) sometime in the spring. I'm not looking forward to that drive. I may tow it.

The timing chain on mine has stretched enough that you can hear it "knocking" a bit. I thought it was a piston knocking but a mechanic identified the chain as the culprit. I'm overseas right now, so I'll have him change it for me.

I have installed a cold air kit on it and I'll probably replace the distributor cap, wiring, etc soon. I do have an electric fan for it but it is still in the box. I might install it in December when I am home on leave. I doubt I will do anything more than that. Ill give it to my son as his first vehicle next year and get myself a 6 cylinder version.
Hey once you are done changing all of that stuff if you dont mind and remember could you send me a PM telling me if there is a major difference and if it is worth doing.
 

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Discussion Starter #9
Hey once you are done changing all of that stuff if you dont mind and remember could you send me a PM telling me if there is a major difference and if it is worth doing.
I'll do my best. The intake replacement had almost zero affect, according to my daughter who had to drive it from Colorado to Arizona. I doubt the timing chain or distributor will have an affect, I just don't like the noise and it is just a tune up type of change. The electric fan might have an affect but I won't be making the change until December. It is only worth about 20 horses at best, according to other threads I have read.
 

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20 horses?! It's likely closer to 10 at the very most, best case scenario. With the MPFI, you are likely to see 20-25hp at the most with all of the things you can do, some claim they have seen 45hp.
 

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When i first got my jeep i was devastated with the crappy 2.5. It was 2 hours on a highway from where i bought it to my place and i got a taste for its...less than desirable performance. But frankly thats just the way it is. Ive learned to love it. Ive added a few mods like E fan, cold air intake, tb spacer, 4.0 throttle body, magnaflow exhaust, firepower ignition. None of which provided much boost in power by themselves but altogether they have provided a decent boost. Not like an extra two cylinders worth or anything but its much more peppy.

This being said, the 2.5's off road performance is stellar. I have not had a problem yet. I have stock gears and i'm pulling 33's underneath on a 4" lift and it does really well. The off road performance is great and that is what really matters to me.

Someone somewhere on one of these forums said it best: i can't go anywhere very fast, but i can go anywhere i want.
 

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I have had my 85 YJ for about two months now and have put on a little over 1200 mostly highway miles. I have said this in other 2.5l threads, but I am now completely convinced that at some point my Jeep was re-geared. I have absolutely no trouble at all getting to and maintaining 80mph on the freeway without having to mash the pedal to the ground.
At first I thought that the gauge was not calibrated, but I used my phone GPS to map the speed and its pretty close (actually at 80 on the gauge I am going 84).
Without opening it up, is there a way to tell what the gearing is?
 

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Discussion Starter #13
Maybe that is what I need to do. Any recommendations or advice on changing the gears? I'll crack open the rear diff when I am home and see what they are.
 

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They come with 4:10s and with 33s I am slow. Regearing to 4:88s is expensive about $1200-1500 in a shop. I am still looking and have no problem running slow on the highway or uphill the drive is that much more scenic. Weekend Jeep not a DD.
 

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gearing

The gearing is a combination of the transmission, transfer case, rear end, and tire size. It is very simple to change the gearing when needed, even when driving. It is called, shifting gears.

Fifth gear is an overdrive. Try running in 4th gear on the interstate. Watch the RPM's. You will find that the RPM's are quite reasonable, even at 75 on the interestate with stock tires. It won't hurt it one bit to run it at 3500 or 3700 rpm.

Give it a try and let us know how it works. Of course it will be noisier on the engine. More so than on a standard car because of the lack of body integrity on the Jeep.

I've had my 95 YJ, 2.5 since 95. I towed my 29' trailer with it and ran at 70-75 on the interstate with it. It is still going strong and the engine runs like new. Still on original clutch and transmission.
 

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My engine has 125k on it and it pulls the 31's just fine at 75+. After reading forums I was nervous at first but I have taken it up to 80 and it probably had more in it. The gear ratios are stock and I have verified the speedo with my gps as well. Not sure why some have so much difficulty and others do not.

I either want to plan a diesel swap or turbo the 2.5 as I have problems with how long it takes to get up to speed, but not actually maintaining it. It comes from being used to my gto's massive amounts of torque.
 

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I have a 4.0 94 and if i hit a hill at 70 ill drop like a rock down to 60-55 so i know your pain. is 3500 really a decent rpm for just the 2.5 or both that and 4.0 by chance? usually once i hit about 65 in 5th im at 2000 rpm, and my gas gauge will start dropping like crazy, but im interested in trying 4th.
 

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red line

Just watch the redline and stay about 750 rpm below the redline. That is what the redline is for, to stay below but ok to run below that.

There is far less wear on the bearings running at 4,000 rpm than there is at 2500 rpm under a heavy load. There has to be so much work produced during a given period of time by each cylinder. If that work has to be done in one revolution that is so much thrust on the bearing. If it can be done in 2 revolutions, that is 50% less on each revolution.

Try sanding something and increasing the pressure by 100%. A LOT mre wear. Same applys to the pressure between the bearing and journal.

I ran mine all the way from Sturgis, SD Jeep Rally to Minneapolis at about 4,000 rpm with the trailer behind. Ran fine and still does.

Talk to a long term over the road trucker that runs gas rigs. Not diesel because those are built to different standards. They will tell you, keep the rpms up and keep the engine in its high torque band. You will actually get better gas mileage running at the higher rmp as the engine is more efficient.
 

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Just watch the redline and stay about 750 rpm below the redline. That is what the redline is for, to stay below but ok to run below that.

There is far less wear on the bearings running at 4,000 rpm than there is at 2500 rpm under a heavy load. There has to be so much work produced during a given period of time by each cylinder. If that work has to be done in one revolution that is so much thrust on the bearing. If it can be done in 2 revolutions, that is 50% less on each revolution.

Try sanding something and increasing the pressure by 100%. A LOT mre wear. Same applys to the pressure between the bearing and journal.

I ran mine all the way from Sturgis, SD Jeep Rally to Minneapolis at about 4,000 rpm with the trailer behind. Ran fine and still does.

Talk to a long term over the road trucker that runs gas rigs. Not diesel because those are built to different standards. They will tell you, keep the rpms up and keep the engine in its high torque band. You will actually get better gas mileage running at the higher rmp as the engine is more efficient.
The 2.5L makes its peak torque at 3500rpm, above that and you're blowing gas out your tailpipe. Also, the lower the RPM's, the more efficient your engine is. Why do you think modern vehicles have overdrive gears?
 
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