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Offline kingofkings

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need motor help
« on: July 09, 2010, 11:09:43 PM »
about 2 wks ago i started to notice major power loss in my 2.5l on the highway.  all of a sudden fifth gear became almost useless and i was losing power in 4th also.  it got worse till last week i could feel the jeep lightly bucking when i was bogging the motor even the slightest. sometimes even backfiring.    i then replaced the plugs wire and cap, (the rotor didnt look to bad)  it felt a littlle better but didnt last to long till i noticed the same syptoms.   i dont know where to start looking first thought i would ask for advice on here.          i have done the 4.0 tb on it 4 or 5 months ago and put a cherry bomb glasspack on 6 months ago.  those are the only motor mods.     i dont know if my maybe my fuel pump is going or injectors are clogging or intake is messed up.   just to many options hoping someone might have a little insight.     thanks in advance for any help
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Offline Jeffy

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Re: need motor help
« Reply #1 on: July 09, 2010, 11:15:35 PM »
Check for codes?
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Offline sharpxmen

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Re: need motor help
« Reply #2 on: July 09, 2010, 11:31:26 PM »
catalytic converter or fuel pressure (pump or filter) most likely

when was the last time you replace the cat and fuel filter? if so far back that you can't remember it's safe to do both as you will need to do those soon anyway.

hope this helps
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
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Offline kingofkings

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Re: need motor help
« Reply #3 on: July 10, 2010, 06:22:42 AM »
well its not throwing any codes.     and the motor only has 81000 on it do you really think the cat would go bad that quick?
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Offline sharpxmen

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Re: need motor help
« Reply #4 on: July 10, 2010, 09:09:18 AM »
Quote from: kingofkings on July 10, 2010, 06:22:42 AM
well its not throwing any codes.     and the motor only has 81000 on it do you really think the cat would go bad that quick?

yeah, they usually last 200,000 miles  :nono:

EDIT: mine has less than that and i replaced it twice, the first time it failed emissions, the second time it broke inside and blocked the exhaust so bad that i could not drive faster than 20 (no exaggeration). The fuel filter should be replaced for sure if you didn't yet, the cat should also be replaced anyway at that many miles so might as well do it, can't tell you for sure that's the problem but is pretty close to what you describe as far as behavior to either lack of fuel or clogged cat
« Last Edit: July 10, 2010, 09:22:26 AM by sharpxmen »
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Offline kingofkings

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Re: need motor help
« Reply #5 on: July 10, 2010, 05:55:15 PM »
well i hooked it up to the fuel pressure guage at work and looked up the specs on it.  was only running 2psi low from max.   so i guess i can rule fuel as a problem.  all the mechanics are saying its prob the cat.     think tommorrow i will pull it off and gut it and see what hapens
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Offline sharpxmen

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Re: need motor help
« Reply #6 on: July 10, 2010, 06:06:49 PM »
Quote from: kingofkings on July 10, 2010, 05:55:15 PM
well i hooked it up to the fuel pressure guage at work and looked up the specs on it.  was only running 2psi low from max.   so i guess i can rule fuel as a problem.  all the mechanics are saying its prob the cat.     think tommorrow i will pull it off and gut it and see what hapens
yeah, go with the cat first as seems to be that, but...

was that 2psi low at idle? if that's the case you have a fuel problem too. under load you use a lot (and i mean a lot literally) more fuel than at idle, so if you're 2psi lower than specs there could be way more lack of fuel under load - keep in mind that also you could have enough pressure when idling but not enough flow, so once you actually floor it that lack of flow will translate in even lower pressure.
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Torch_Ind

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Re: need motor help
« Reply #7 on: July 10, 2010, 06:23:24 PM »
easy way is run it with the fuel gauge tied to the wiper arm "don't do it in the rain"  or pull the front o2 sensor out and see if your power comes back because you have somewhere for the exhaust to escape and not have so much back pressure. 
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Offline kingofkings

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Re: need motor help
« Reply #8 on: July 11, 2010, 03:45:08 PM »
the fuel pressure was 2 pounds less than absolute max pressure.   it was still well above specs.     I had a chance to change the cat out today and it made a world of difference.   $100 for the new cat all the piping and clamps i needed so im happy with it.    plus it got a little throatier rumble to it no.   :dance:
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