2001 TJ loses power and acceleration going up hills

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Black and Yellow

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Jun 22, 2021
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San Jose California
Hey all,

I recently purchased my 2001 jeep TJ and I realized that when it goes up hill it will not go past 2800-3000 rpm and will not accell, even with the gas pedal is all the way down. This is on highway's and other paved roads and not off -roading or on gravel or sand. I am running a 2.5L engine with 30" tires. The vehicle drives well on flat roads but for instance on a 4000 foot incline to Tahoe I cannot get a speed higher than 44-55 mph. I was curious if anyone else has this problem or is this a TJ thing I have just to deal with.

I will take it to a proper mechanic but also want to reach out to the community to make possible trouble shooting a litter easier. Any information would be greatly appreciated.

Thank you and Cheers.
 
It's the 120 hp 2.5L engine trying to turn those 30" tires that is giving you a headache. If you re-geared to a proper ratio, it would solve your problem.
 
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JMT said:
It's the 120 hp 2.5L engine trying to turn those 30" tires that is giving you a headache. If you re-geared to a proper ratio, it would solve your problem.
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X2 to this. This is exactly your issue.
 
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Your Jeep is fine, these guys generally love to hate on the smaller displacement Jeeps. Feel free to ignore their comments, they'll probably go on and on. You probably need a tune-up or basic service. Your Jeep can maintain speeds well above what you have stated. Not going past 2800 rpm is completely not normal and any experienced mechanic will 100% agree.
 
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pagrey said:
Your Jeep is fine, these guys generally love to hate on the smaller displacement Jeeps. Feel free to ignore their comments, they'll probably go on and on. You probably need a tune-up or basic service. Your Jeep can maintain speeds well above what you have stated. Not going past 2800 rpm is completely not normal and any experienced mechanic will 100% agree.
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Who hated on the 2.5L in this thread? I just read the whole thread again to make sure I wasn't delusional. Most of it is informational only. One comment says it's a turd, but adds that a 4.0 isn't much better.
 
JMT said:
It's the 120 hp 2.5L engine trying to turn those 30" tires that is giving you a headache.
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This specifically. The headache has to do with the fact the engine cannot rev past 3000 rpm which is clearly stated in the first post. Every single bit of advice about the 2.5L engine since the dawn of time revolves around revving the engine out to make power, how do you do that if it is stuck below 3K?

Edit: Sorry, @JMT, these smaller displacement Jeeps get allot of flack, no need to go off on you
 
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pagrey said:
This specifically. The headache has to do with the fact the engine cannot rev past 3000 rpm which is clearly stated in the first post. Every single bit of advice about the 2.5L engine since the dawn of time revolves around revving the engine out to make power, how do you do that if it is stuck below 3K?
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I wouldn't classify that as "hating on a smaller displacement jeep" on any day of my life.

The thing we don't know from the OP is what degree climb this hill is up to Tahoe. He says he has the pedal to the floor. If it's as steep as he is implying, perhaps as he starts the hill the rpm's drop since they can't maintain over 3,000rpm at 44-55mph. Or, as you are implying, something is wrong with the engine because no matter how steep it is the 2.5 should be able to maintain over 3000rpm. It might be able to in 4L at sub 5mph, but there is a cutoff somewhere in it's ability to do that.
 
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Jumping in here. Yes my tiny 2.5L should perform just fine. I have been pass by by cars and yes some jeeps just as old as mine cruzing along at 4000 feet. And while a basic tune up is for sure scheduled and needed, I cannot deny that 2+ inches of tires would require a regearing that I was hoping to avoid. I did really thing that what I had was original speck tires
JMT said:
That year the 2.5 came with either a 205/75r15 or 225/75r15

Equivalents: 27.1 or 28.3

They are just anemic
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That actually explains a lot. My current tires are wider and bigger. Thanks for the Heads up.
. Maybe the previous owner did no know as much. After I report to a mechanic I will update this thread.
 
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Black and Yellow said:
Jumping in here. Yes my tiny 2.5L should perform just fine. I have been pass by by cars and yes some jeeps just as old as mine cruzing along at 4000 feet. And while a basic tune up is for sure scheduled and needed, I cannot deny that 2+ inches of tires would require a regearing that I was hoping to avoid. I did really thing that what I had was original speck tires

That actually explains a lot. My current tires are wider and bigger. Thanks for the Heads up.
. Maybe the previous owner did no know as much. After I report to a mechanic I will update this thread.
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The straight 4 likes rpm’s just as much as the straight 6. If it can’t get over 2850 or so, it’s not going to pull a hill.
 
Yep don't be afraid to wind it out on hills. Don't look at the tach on a regular car with small tires and think those rpms are also appropriate on a Wrangler with big tires and aerodynamics like a barn door. I regularly get mine to 4K and wouldn't be afraid to go higher if needed.
 
Black and Yellow said:
Hey all,

I recently purchased my 2001 jeep TJ and I realized that when it goes up hill it will not go past 2800-3000 rpm and will not accell, even with the gas pedal is all the way down. This is on highway's and other paved roads and not off -roading or on gravel or sand. I am running a 2.5L engine with 30" tires. The vehicle drives well on flat roads but for instance on a 4000 foot incline to Tahoe I cannot get a speed higher than 44-55 mph. I was curious if anyone else has this problem or is this a TJ thing I have just to deal with.

I will take it to a proper mechanic but also want to reach out to the community to make possible trouble shooting a litter easier. Any information would be greatly appreciated.

Thank you and Cheers.
Click to expand...
I've been running 31's for years with my 2.5 and as Jerry stated wind her up. I have no issues on the rather vertical roads around here in 4th with a little third thrown in now and then. If she is up to snuff no reason not to get her going.
 
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Black and Yellow said:
Hey all,

I recently purchased my 2001 jeep TJ and I realized that when it goes up hill it will not go past 2800-3000 rpm and will not accell, even with the gas pedal is all the way down. This is on highway's and other paved roads and not off -roading or on gravel or sand. I am running a 2.5L engine with 30" tires. The vehicle drives well on flat roads but for instance on a 4000 foot incline to Tahoe I cannot get a speed higher than 44-55 mph. I was curious if anyone else has this problem or is this a TJ thing I have just to deal with.

I will take it to a proper mechanic but also want to reach out to the community to make possible trouble shooting a litter easier. Any information would be greatly appreciated.

Thank you and Cheers.
Click to expand...
Auto or manual transmission? Have you tried shifting to a lower gear?
 
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TJ4Jim said:
I've been running 31's for years with my 2.5 and as Jerry stated wind her up. I have no issues on the rather vertical roads around here in 4th with a little third thrown in now and then. If she is up to snuff no reason not to get her going.
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Fellow 31's on the 2.5 chiming in...
In my experience, extended steep inclines pretty much have to be tackled in 3rd gear. For brief inclines (maybe a quarter mile or so) 4th or 5th will get the job done if you are already at speed. I'll definitely do 45-55 in 3rd gear on a steep ascent, and could probably do more if I really wanted. Realistically though, I'm probably not running over 55 in 3rd, and 4th isn't going to get me anywhere on a prolonged grade.
 
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Hey reporting back in. I have visited a mechanic and the jeep got a clean bill of health on the exhaust and engine over all. Next up is to find someone in the bay area the knows re-gearing. And to update on the ties now that I have had a close inspection mine are tire 30x9.50r15lt. A pretty meaty tire if my vehicle has never been re-geared.
 
Black and Yellow said:
Hey reporting back in. I have visited a mechanic and the jeep got a clean bill of health on the exhaust and engine over all. Next up is to find someone in the bay area the knows re-gearing. And to update on the ties now that I have had a close inspection mine are tire 30x9.50r15lt. A pretty meaty tire if my vehicle has never been re-geared.
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That 3 tire sizes over the basic stock size of 27,s so 3 inches. I would think weight would be a factor going up hill , can you reduce weight before you re gear?
Your profile shows Auto by the way :)
 
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