jeep sluggish but power jumps notice ably at 3k rpms
04-14-2011, 01:33 PM
#1
jeep sluggish but power jumps notice ably at 3k rpms
My 1992 Jeep Cherokee (4.0L sport) seems seriously under-powered until I crank it up over 3k rpms - then it noticeably "leaps" forward. Enough that i can feel the kick (acceleration) when it crosses the line to 3k rpms.
It has me wondering if its a CPU or chip issue ... or possibly some cylinders not firing 100% or something equally unusual.
Odd thing is I tried pulling plug wires 1 at a time ... to see if the engine idles differently. However, it seemed to make no difference at an idle -- so was at a loss as how to determine if a cylinder isn't firing 100%.
Any ideas what could cause the lack of power under 3k RPMs and sudden boost once it passes 3K ?
Some notes:
* Replaced ignition system with the 4.0 Firepower kit and gap'd plugs to 0.65 (kit included cap, wires, coil, etc)
* My O2 sensor is disconnected ... wire was ripped off when wheeling. Issue existed before this happened, so haven't bothered repairing.
* Engine is in good shape, was rebuilt about 30k miles ago
* Rear drive line replaced with SYE + Tom Woods custom Drive shaft.
It has me wondering if its a CPU or chip issue ... or possibly some cylinders not firing 100% or something equally unusual.
Odd thing is I tried pulling plug wires 1 at a time ... to see if the engine idles differently. However, it seemed to make no difference at an idle -- so was at a loss as how to determine if a cylinder isn't firing 100%.
Any ideas what could cause the lack of power under 3k RPMs and sudden boost once it passes 3K ?
Some notes:
* Replaced ignition system with the 4.0 Firepower kit and gap'd plugs to 0.65 (kit included cap, wires, coil, etc)
* My O2 sensor is disconnected ... wire was ripped off when wheeling. Issue existed before this happened, so haven't bothered repairing.
* Engine is in good shape, was rebuilt about 30k miles ago
* Rear drive line replaced with SYE + Tom Woods custom Drive shaft.
04-15-2011, 12:02 AM
#2
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Join Date: Mar 2011
Location: Arlington TX.
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Year: 1996
Model: Cherokee
Engine: 4.0
My 96 does the exact same thing. Thats just where the power band kicks in and starts making its power. Or thats what Im thinking anyway!
04-15-2011, 12:11 AM
#3
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Location: Lima Ohio
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Year: 1996
Model: Cherokee
Engine: 4.0 HO
My 1992 Jeep Cherokee (4.0L sport) seems seriously under-powered until I crank it up over 3k rpms - then it noticeably "leaps" forward. Enough that i can feel the kick (acceleration) when it crosses the line to 3k rpms.
It has me wondering if its a CPU or chip issue ... or possibly some cylinders not firing 100% or something equally unusual.
Odd thing is I tried pulling plug wires 1 at a time ... to see if the engine idles differently. However, it seemed to make no difference at an idle -- so was at a loss as how to determine if a cylinder isn't firing 100%.
Any ideas what could cause the lack of power under 3k RPMs and sudden boost once it passes 3K ?
Some notes:
* Replaced ignition system with the 4.0 Firepower kit and gap'd plugs to 0.65 (kit included cap, wires, coil, etc)
* My O2 sensor is disconnected ... wire was ripped off when wheeling. Issue existed before this happened, so haven't bothered repairing.
* Engine is in good shape, was rebuilt about 30k miles ago
* Rear drive line replaced with SYE + Tom Woods custom Drive shaft.
It has me wondering if its a CPU or chip issue ... or possibly some cylinders not firing 100% or something equally unusual.
Odd thing is I tried pulling plug wires 1 at a time ... to see if the engine idles differently. However, it seemed to make no difference at an idle -- so was at a loss as how to determine if a cylinder isn't firing 100%.
Any ideas what could cause the lack of power under 3k RPMs and sudden boost once it passes 3K ?
Some notes:
* Replaced ignition system with the 4.0 Firepower kit and gap'd plugs to 0.65 (kit included cap, wires, coil, etc)
* My O2 sensor is disconnected ... wire was ripped off when wheeling. Issue existed before this happened, so haven't bothered repairing.
* Engine is in good shape, was rebuilt about 30k miles ago
* Rear drive line replaced with SYE + Tom Woods custom Drive shaft.
change your tranny filter an look if there alot of metal or junk in the fluid and if that dosent fix it then it could be your tourque converter
04-15-2011, 02:22 AM
#4
5 speed
Does that apply only for auto trans ?
forgot to mention;
its a 5 speed manual transmission
front/rear axles were swapped from stock 3.55 to 3.73 from another XJ
forgot to mention;
its a 5 speed manual transmission
front/rear axles were swapped from stock 3.55 to 3.73 from another XJ
Last edited by sgt_why; 04-15-2011 at 02:27 AM.
04-15-2011, 11:44 AM
#5
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Join Date: Apr 2011
Location: Lima Ohio
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Year: 1996
Model: Cherokee
Engine: 4.0 HO
lol oh yea then ur in the clear in that department id say check fuel filter and injectors and mabye sum new plugs and wires
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04-16-2011, 05:21 PM
#8
tried all the obvious stuff
My thought was that it might be related to the missing O2 sensor -- but replacing it seemed to make no difference.
Last fall
- replaced fuel filter
- replaced all the fuel injectors with complete new injectors
Last spring
- the cap & rotor were replaced with new ones included in the firepower 4.0l kit ... cap & rotor, fitted high temp plug wires, new plugs gap'd to 0.65
http://www.performancedistributors.com/jeep4.0.htm
--
Maybe will have to pull the plugs and take a look ... see if any look worse than the others? Not sure what else to check
Could it somehow be related to the change from 3.5 -> 3.73 gear ratios in the axles ??
Last fall
- replaced fuel filter
- replaced all the fuel injectors with complete new injectors
Last spring
- the cap & rotor were replaced with new ones included in the firepower 4.0l kit ... cap & rotor, fitted high temp plug wires, new plugs gap'd to 0.65
http://www.performancedistributors.com/jeep4.0.htm
--
Maybe will have to pull the plugs and take a look ... see if any look worse than the others? Not sure what else to check
Could it somehow be related to the change from 3.5 -> 3.73 gear ratios in the axles ??
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