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Old 07-07-2014, 02:38 PM   #1
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2000 4.0L lacking power???

So, this may just be my over-expectation for the performance of my 2000 4.0L manual, but is anyone else experiencing a lack of power on the top end? You would think with the wrangler being relatively small for a big 4.0 6cyl, in-line at that, that it should have plenty of power for tackling interstate inclines at 70mph and be able to maintain speed. However, I have noticed a tremendous lack of power, or at least I think so. The other day I took a quick trip to Asheville, NC from Tri-Cities, TN and it was all I could do to keep my speed up going over the mountain. I had to drop it down to 4th numerous times. And this is on I-26, not a ridiculously steep or curvy mountain road. I have also noticed a tremendous drop in power when turning on the AC. I would expect a slightly noticeable difference, but this just seems too far. Has anyone else experienced this? If so, was it something perhaps with plugs/wires that a tune up could fix? Or even the cat? Or are my expectations for this 4.0 sport just too high?

Thoughts.........thanks.

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Old 07-07-2014, 02:43 PM   #2
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What size tires are you running, and what gearing? Best way to lose power is larger tires and stock gearing. I went from 31s to 33s with 3.73 gear and notice a big hit when on long Streep grades on the interstate.

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Old 07-07-2014, 03:57 PM   #3
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I'm running the stock 30x9.5x15. The guy I bought it from was running 31x10.5x15 so I've downsized. Gear ratio I would have to look up. It's got the 44 rear so I'm thinking 3.73 gearing also.
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Old 07-07-2014, 04:08 PM   #4
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Any engine codes? With 3.73s and 30" tires, it should be pretty spunky.
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Old 07-08-2014, 07:48 AM   #5
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I'm running it by the mechanic this week to check for codes. It has plenty of spunk on the lower end, but it just seems to run out too early on the high end in 5th and definitely won't maintain in 5th on any kind of larger incline.
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Old 07-08-2014, 08:53 AM   #6
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Did the 2000 model have the ignition trick with the key to check codes? Been a while since I've done it, but u should be able to read them without a dedicated reader. I'd have to search it up, but I think it was turning the key on and off 3 times in a row would display codes in the odometer window....
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Old 07-08-2014, 09:19 AM   #7
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Did the 2000 model have the ignition trick with the key to check codes? Been a while since I've done it, but u should be able to read them without a dedicated reader. I'd have to search it up, but I think it was turning the key on and off 3 times in a row would display codes in the odometer window....
Now that you mention it, I recall seeing something about that a while back. I'll look it up and try it during lunch.
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Old 07-08-2014, 09:45 AM   #8
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The 4.0 is a dog. You need to drive it like a civic, and keep the rpms up.
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Old 07-08-2014, 03:39 PM   #9
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Any engine codes? With 3.73s and 30" tires, it should be pretty spunky.
No codes using the in-cab method by turning the switch 3 times while holding the odometer reset.
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Old 07-08-2014, 06:26 PM   #10
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I've got a 2001 TJ with 87000 m. on it and when I first bought it too was a dog. It's got 32" tires on it so I had it regeared to 4.10's and it's a totally different Jeep! It'll cruise 70 up some steep grades. Also, I changed out the spark plugs (old one's look original with about a 1/4 gap!)and that helped a ton too.
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Old 07-08-2014, 11:02 PM   #11
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I have a 2000 4.0 5speed with 3.73 gears on 33x10.5 tires and I can accelerate on steep high way hills. Im in 4th or 3rd gear though. What gear are you in when try to maintain high way speed?
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Old 07-08-2014, 11:13 PM   #12
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Yes it's weak on highway. Your issue with those gears and tires is good. Nothing to be fixed. Live with it. Or get a sports car. It looks like a brick for a reason. It likes to trade HP with the wind.
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Old 07-09-2014, 07:34 AM   #13
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I have a 2000 4.0 5speed with 3.73 gears on 33x10.5 tires and I can accelerate on steep high way hills. Im in 4th or 3rd gear though. What gear are you in when try to maintain high way speed?
I'm in 5th gear, about 2300 rpm at 70. Maybe I got a good one but I'm happy with my 4.0 now. It has all the power I need.
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Old 07-09-2014, 09:06 AM   #14
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Originally Posted by TJspeed View Post
I have a 2000 4.0 5speed with 3.73 gears on 33x10.5 tires and I can accelerate on steep high way hills. Im in 4th or 3rd gear though. What gear are you in when try to maintain high way speed?
I'm in 5th rolling down the highway at 70-75, but once I hit a hill of good stature it'll drop to 60 in no time with pedal on the floor so I have to kick it into 4. I just imagined the 4.0 would maintain a little better than that. I'm going replace plugs and wires and go from there.

All in all, I'm fine with changing gears. I'm not fine with changing vehicles. Unless of course it's just upgrading to another Wrangler eventually.
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Old 07-09-2014, 09:09 AM   #15
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Originally Posted by cornfieldtj View Post
I've got a 2001 TJ with 87000 m. on it and when I first bought it too was a dog. It's got 32" tires on it so I had it regeared to 4.10's and it's a totally different Jeep! It'll cruise 70 up some steep grades. Also, I changed out the spark plugs (old one's look original with about a 1/4 gap!)and that helped a ton too.
What did the re-gearing end up costing? And how did it affect your lower gears/speeds?
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Old 07-09-2014, 09:16 AM   #16
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I'm in 5th gear, about 2300 rpm at 70. Maybe I got a good one but I'm happy with my 4.0 now. It has all the power I need.
That's your problem. 2300 rpms on the freeway is only good for flat ground. You need to drive it like a little 4 banger and keep the rev's up. It should pull around 3500+ just fine.
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Old 07-09-2014, 06:20 PM   #17
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What did the re-gearing end up costing? And how did it affect your lower gears/speeds?
$1900 for a sye, 8.8 conversion, 4.10's and a eaton suretrac for the front axle, all installed. But I'm buddies with one of biggest ring and pinion sellers in the nation. I got a deal.
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Old 07-09-2014, 06:29 PM   #18
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That's your problem. 2300 rpms on the freeway is only good for flat ground. You need to drive it like a little 4 banger and keep the rev's up. It should pull around 3500+ just fine.
I could be off on that 2300 rpm. Could be somewhat higher as I don't drive 70 mph very often, my jeep gets real twitchy at that speed. But she just cruises uphill effortlessly.
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Old 07-10-2014, 12:25 PM   #19
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$1900 for a sye, 8.8 conversion, 4.10's and a eaton suretrac for the front axle, all installed. But I'm buddies with one of biggest ring and pinion sellers in the nation. I got a deal.
Wowza! I'd hate to see a non-deal price. I think I'll just have to keep it in 4th for now and see what a good solid tune-up does. Thank for the info.

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