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Author Topic: Jeep TJ power loss  (Read 111 times)

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Offline Jrama

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Jeep TJ power loss
« on: July 15, 2020, 05:17:29 PM »
Hey everyone,

I have a sudden loss of power, feels like I lost 75hp. No check engine (apart from the evap code that is always there). Power loss is more noticeable at higher rpms. No smoke, no noises, runs smoothly, starts no problem, oil is good (No flakes, foam, etc.), no signs of blow by etc. In Neutral it doesn't easily reach the limiter, it wouldn't even go past 4200 at one point ( sounded like it was bouncing off the limiter at 4200). After the full tank (noted Below) It will get to the limiter kinda weakly.

 I figured I might have gotten some water in the gas a few weekends ago doing a deep river crossing. The tank finally got down to below a quarter full and I figured it was probably sucking some water. So I added some water remover and put in a full tank, its a bit better but not nearly where it should be power wise.

What are come common things to check out? Engine is a 4.6 stroker (All same accessory's etc. as 4.0)

To me it might still be a fuel issue? Maybe a clogged cat? Any pointers on what to check is appreciated.

Cheers

Offline hps4evr

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Re: Jeep TJ power loss
« Reply #1 on: July 15, 2020, 09:33:36 PM »
Kinda sounds like a plugged cat con. They can do this, especially under load.
Fuel pressure could be falling off too at higher rpm. Would have to test to confirm.
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Offline Vinman

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Re: Jeep TJ power loss
« Reply #2 on: July 16, 2020, 10:15:24 AM »
Could also be a plugged air filter
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Quote from: Bnine link=topic=25904.msg162940#msg162940      date=1341881306

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Offline Jrama

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Re: Jeep TJ power loss
« Reply #3 on: July 16, 2020, 04:53:09 PM »
I checked the filter already and it does need changing but its fine.

I am going to pursue the plugged cat/muffler idea (I have only pre-cats). I will pull the 2 upstream sensors and see if there is an improvement in performance.

Offline rws

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Re: Jeep TJ power loss
« Reply #4 on: July 16, 2020, 05:41:17 PM »
I checked the filter already and it does need changing but its fine.

I am going to pursue the plugged cat/muffler idea (I have only pre-cats). I will pull the 2 upstream sensors and see if there is an improvement in performance.


There is an easy way to check cat.conv. with a temperature gun.   Easy to google and find methods.

Offline Jrama

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Re: Jeep TJ power loss
« Reply #5 on: July 21, 2020, 01:56:56 PM »
So there was a major temperature difference between the two pre-cats, and sure enough the one with the much lower temp was completely blocked.

One Question I have is if the bolts that hold the pre-cat to the exhaust manifold are not completely tight...could that be a possible cause for cat failure?...They were loose-ish.

Jeep only has 140K kms, seems premature for a failure like this, then again before I rebuilt the motor is was burning a ton of oil. There was little to no smoke coming out of the tailpipe out the time ??? Maybe that destroyed the cat?

Offline Vinman

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Re: Jeep TJ power loss
« Reply #6 on: July 21, 2020, 02:44:07 PM »
I do believe excessive oil consumption will indeed plug the cats eventually.
/l ,[____],
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Quote from: Bnine link=topic=25904.msg162940#msg162940      date=1341881306

 Resident prick is my job and it took me ten years to earn that title

Offline Jrama

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Re: Jeep TJ power loss
« Reply #7 on: July 27, 2020, 07:08:20 PM »
Got the new Pre-Cat from Rock Auto, ordered Monday arrived Thursday. Jeep definitely has a bit more spunk than than with the old cat (before the clog)

Offline MattMan

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Re: Jeep TJ power loss
« Reply #8 on: July 28, 2020, 06:43:47 PM »
 8)  Good to hear!
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