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Unread 01-28-2013, 02:41 PM   #1
PoundHipster
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2005 KJ Liberty 
 
Join Date: Nov 2012
Location: Boulder, Colorado
Posts: 23
High End Power with 3.7

Hey All-


I have a 2005 KJ 3.7L and was wonder what kind of power I should be expecting to have at high speeds and on inclines. I live in the foothills and do a lot of driving in the Rocky Mountains and have been pretty disappointed with the power I am getting at high speeds and especially while going up hills and mountains. Seems like I have barely any power.

Before this Fall I had a 2000 XJ 4.0L and I never felt like I was underpowered, but I lived in upstate NY and the Adirondacks are hardly the Rocky Mountains.

Stat sheets tell me my 3.7 has more power and torque than the 4.0, but I am not really feeling it. Should I look to replace spark plugs, etc, or is this just the difference between the Cherokee and the Liberty?

Thanks in advance!
Geo

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Unread 01-28-2013, 06:14 PM   #2
tommudd
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2004 KJ Liberty 
 
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When was the last tuneup? If its been 30,000 miles or so then yes throw some good copper core plugs in, it may help
Also make sure all maintenance is up to date
What type and size tires/ tire pressure etc makes a difference
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Unread 01-28-2013, 06:27 PM   #3
kirksjeep
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I too just switched my DD from and XJ to a KJ. I agree that the KJ doesn't feel like it has the same get up and go as the XJ, but I think it has more to do with the computer controlled transmission then anything else. Try driving it hard for a few days and the engine will wake up.
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Unread 01-28-2013, 07:37 PM   #4
olliehopnoodle
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It does seem to lack the torquey feel and when you get on it the transmission jumps you up to a higher RPM but I think this was by design. It 'sounds' like it is strugglinng but in actuality it is doing okay. Certainly not a major power house of an engine though.
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Unread 01-28-2013, 08:58 PM   #5
PoundHipster
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Tommudd - I just got her in October, so I am not sure of what maintenance has been done, but I am coming up on the 90k service interval so I figured spark plugs should be replaced (should I definitely replace anything else?). It has 235/70s on it right now, but the spare is 225/75 so I figure it came with 225/75 from the factory. Would this make a difference? I keep the psi at the recommended level (tires are Dynapro ATM/ my xj had Destination A/Ts).

kirksjeep - I usually drive it pretty spiritedly, so I would think the computer would have adapted?

olliehopnoodle - I think the trans jumping is different from the XJ because of the O/D in the KJ. But even when it jumps back into 4 it pretty much plateaus with power.

I think my next step is going to be spark plugs, thanks for the input!
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Unread 01-28-2013, 09:37 PM   #6
BobFromCO
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2006 KJ Liberty 
 
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FWIW, 235/70 16's are actually the OEM size, so I think the spare is the odd man out.
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Unread 01-29-2013, 09:51 AM   #7
DaveJKJ
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Quote:
Originally Posted by PoundHipster View Post
Hey All-


I have a 2005 KJ 3.7L and was wonder what kind of power I should be expecting to have at high speeds and on inclines. I live in the foothills and do a lot of driving in the Rocky Mountains and have been pretty disappointed with the power I am getting at high speeds and especially while going up hills and mountains. Seems like I have barely any power.

Before this Fall I had a 2000 XJ 4.0L and I never felt like I was underpowered, but I lived in upstate NY and the Adirondacks are hardly the Rocky Mountains.

Stat sheets tell me my 3.7 has more power and torque than the 4.0, but I am not really feeling it. Should I look to replace spark plugs, etc, or is this just the difference between the Cherokee and the Liberty?

Thanks in advance!
Geo
I live in the Adirondack area and have no problem but I do have to lock out o/d at times depending. I do have bigger tires though and no re-gear so that makes a difference. I have also driven in the Rockies and they are way bigger as you say but maybe it is also the altitude there and the lower octaine gas they sell if I recall right?

Otherwise for more power and a Jeep, you need a Hemi GC. I have driven one and they have plenty of power.

Change the plugs and use the OEM, NGK copper core ones and see if it makes a difference. Even if it doesn't they are only $18 or so at NAPA and can't hurt anything.
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Unread 01-29-2013, 09:44 PM   #8
PoundHipster
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Location: Boulder, Colorado
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I wonder if altitude has anything to do with it, since it is significantly higher than NY (range from 5-11k feet). I do always run 87 instead of the apparently "ok" 85 octane.

A Hemi sounds great right now!
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Unread 01-30-2013, 10:26 AM   #9
Chipppy
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2002 KJ Liberty 
 
Join Date: Dec 2011
Location: Huntsville, Alabama
Posts: 151
My 02 with the 45rfe feels much better all over power wise than my 07 with the 42 tranny. The 02 also have a mechanical throttle I believe witch makes the jeep feel much peppier in my opinion. If you don't mind the gas use overdrive up the hills would feel like it has more power since in a different rpm.
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Unread 01-31-2013, 01:33 AM   #10
PanosKJ
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2005 KJ Liberty 
 
Join Date: Jan 2013
Location: Athens, Greece
Posts: 30
...and if the O/D won't help then wait for foursevenKJ's write ups about 3.7 engine swap to GC 4.7 and follow them....I recon is the only solution if you need more power....besides 3.7 consumes a lot of fuel anyway so the swap won't make any difference on consumption level and at the same time, you'll get lots of great power (V8 plus a great transmission set up)......
My KJ is also 05 with 42 transmission so it needs lots of pushing and I'll do the swap no matter what....
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