1997 TJ 2.5l loss of power in 5th gear. - Jeep Wrangler Forum
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Old 03-21-2016, 01:22 PM
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1997 TJ 2.5l loss of power in 5th gear.

Okay so I've done some research on this thread and I've tried some things that have worked for other people. But none have worked for me yet so here's some details on the jeep and my problem. It pretty much kinda started the same day I took my soft top off (i doubt that has anything to do with it) but going up a hill that I could normally do 65 in 5th gear in I noticed my speed would drop from 60 down to 50 when normally before I could go 65 and this is even true on flat interstate my jeep barely wants to go 65 anymore when just a week ago it would go 75. Now I did put bigger tires on it 31x10.5 but I took the interstate on the way home and drive for 3 days after my tires with no problem so that can't be the problem.

I've got a new cat new muffler New 02 sensors down stream and up stream. Fresh oil fresh plugs and wires. And I'm going to get my fuel pump tested this Wednesday any help would be appreciated

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Old 03-21-2016, 01:24 PM
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Also it's a 97 2.5l with the 5 speed manual in it 224,000 miles stock gears

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Old 03-21-2016, 09:06 PM   #3
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I run a 1997 2.5 with a five speed as well. I have stock gears but run 33x12.50 tires. Acceleration is next to nothing after I pass second gear. Still saving for new gears. I have the same problem. Some days I can push my jeep to almost 80 and others it doesn't want to pass 65. I have a CEL code for misfire cylinder 4 so I'm almost positive that's what it is but I'm not sure. I have noticed my jeep runs a lot faster when it's cold out because there is more oxygen in the denser air so more oxygen per cylinder fire. But back to the point, do you have any CEL codes? Also did it ever run over 65 while you still had the 31's on?
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Old 03-22-2016, 11:12 AM   #4
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I have a 97 TJ with a 4.0 5 speed with 235 75 15 tires with over 320,000 miles. Your just running out of power, maybe someone here will suggest a re-gear.

Here is an example:
The best gas mileage for me is with the hard top (20mpg), second best is soft top (18+mpg), and the worst is no top (16-17mpg). The same with engine temperature before I put in a 3 row radiator, I could not drive the Jeep on the highway during the summer with the top down.

Top down must really effect the aerodynamics of a Jeep which is about as aerodynamic as a refrigerator box.
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Old 03-22-2016, 11:24 AM   #5
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I'll agree with previous suggestions that you are probably out of your powerband with the new tires. Also, jeeps have a lot more surface area to create drag with the top down, so that actually can be related to your jeep's inability to maintain speed. I have an 04 Se with the 2.4L and when I went from stock to 31" tires, I lost the ability to go faster than 65-70 or maintain that speed on any incline until I regeared.
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Old 03-22-2016, 06:17 PM
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Thanks for all the replys. Yes I drove it for 3 days straight with the after getting the bigger tires and there wasn't a issue with reaching 75 and maintaining. The only different thing really is that now I took the soft top off, I just didn't thank that would effect the power of my jeep so greatly. I ran a scanner through it and I'm not throwing any codes so that was good. I'll still go ahead and get my fuel pump tested sense I got a appt tomorrow but if it checks out fine I'll just have to chock this one up to the bigger tires warmer air and having the top off. I'll keep you guys posted thanks again.
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Old 03-22-2016, 07:42 PM   #7
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Quote:
Originally Posted by youtubemechanic93 View Post
Thanks for all the replys. Yes I drove it for 3 days straight with the after getting the bigger tires and there wasn't a issue with reaching 75 and maintaining. The only different thing really is that now I took the soft top off, I just didn't thank that would effect the power of my jeep so greatly. I ran a scanner through it and I'm not throwing any codes so that was good. I'll still go ahead and get my fuel pump tested sense I got a appt tomorrow but if it checks out fine I'll just have to chock this one up to the bigger tires warmer air and having the top off. I'll keep you guys posted thanks again.

I hate to say it but a wrangler with the top down is like a vette towing the space shuttle with the parachute deployed.
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Old 03-22-2016, 09:04 PM   #8
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Did you put the top back on and try to go 75 again?
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Old 03-22-2016, 10:10 PM   #9
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Did you change out the speedometer gear after you installed those larger tires?
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Old 03-23-2016, 12:01 AM   #10
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224,000 miles, 2.5 litre engine, stock gears with 31 inch tires, and the top down. And it won't maintain 65 mph going up a hill??? I'm surprised you could even get to 65!

You said it happened after you took the soft top off, but that couldn't be it. Put the top back on and see what happens...you will be surprised! With the top off, the air that your Jeep is trying to plow through now has lots of new places to sit and swirl around, causing lower air pressure. All of that low pressure is trying to suck your Jeep backwards, and you have to compensate with more power. With a 2.5 litre, you just don't have the power to spare...every bit of power you have is being used to keep the thing moving.

Also, if you didn't re-gear the speedometer gears after the tire swap, your speedo will read lower than the speed you're actually doing. Get a GPS speed tracker app on your phone, and check the speedo...that will also play a part in your diagnosing the problem.
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Old 03-23-2016, 11:16 AM   #11
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I have a 97 4.0 5 speed with 3.73 gears and 255/75/17 JK wheels and tires. Mostly drive in 4th on the freeway because 70mph is 2500rpm used a GPS to get correct speed reading.

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