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anyone got any insight on what could make my 2000 4.0 tj sudenly have no balls? i can hardly get it up over 30 mph going up hill. on the interstate its fine it just takes forever for it to get up to speed. i put in new spark plugs, air filter, i wanted to change that fuel filter but the guy at napa said 2000 tj doesnt have a fuel filter. but its running like a vehicle with a bad fuel filter. the guages are all fine and the dummy light isnt on. however the radiator fluid looks like poop water even though i flushed it like 2 months ago.
 

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Sounds to me like the catalytic cnverter is plugged...Hopefully you're still under the 80,000 mile emissions warranty. if not...$$$!
 

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Yup, sounds like a plugged exhaust.

First - use eyeballs - look for crushed or bent spots.
Do you rememember driving it to make it nice and hot, then plunging through mud or water about the same time it started doing that? I think the pipes are double walled pipes. When hot, then cooled rapidly like in a bath, the inner wall collapses while the outer looks fine.

Try something - hook a vacuum gauge to manifold vacuum. Snap the throttle - it should quickly drop to near 0 during the snap. Let go quick right after the R's are high, the vacuum should snap up higher than it was before.
If neither, suspect a plugged exhaust.

You can also disconnect the head pipe and test it - power comes back? - it was plugged.
 
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Ditto on the cat....good troubleshooting suggestions Rich.....

Your engine is fuel injected so there is not that much that can go wrong....but a plugged cat is one thing that usually does not trigger a trouble code in the computer...

One quick test is to put your hand near the exhaust outlet....when you have someone snap the throttle, you should get a lot of air out of it....

If it's not the cat, then I would start suspecting fuel....and I'm sure you have a fuel filter somewhere...FI does not do well with dirt in it.....look back towards the tank on the inside of the frame.....

How many miles on the engine?

And make sure you let us know what the problem was....
 

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Even quicker and easier test. Find your max rpm in a lower gear. The cat can only handle so much volume. You'll do a little better due to the torque you can mulitply ..but you'll still hit a brick wall that will retreat when you shift gears.
 

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[ QUOTE ]
.and I'm sure you have a fuel filter somewhere...FI does not do well with dirt in it....

[/ QUOTE ]

I was thinking the same thing, but doing a parts search, I can't find a filter for a TJ..... interseting. I'd figure they most certainly would have one.
 

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[ QUOTE ]
[ QUOTE ]
.and I'm sure you have a fuel filter somewhere...FI does not do well with dirt in it....

[/ QUOTE ]

I was thinking the same thing, but doing a parts search, I can't find a filter for a TJ..... interseting. I'd figure they most certainly would have one.

[/ QUOTE ]

It's in the tank. It's sorta integrated with the regulator/pump. You can change it ..but the thing is, you probably will never take the tank down unless the pump is null and void. You can get (IIRC) the regulator and filter separate ..but the pump is only available with the other two components (again, IIRC). Hence virtually no one JUST changes the filter.

He can do a pressure check to see if there's a problem there.
 

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A shot of propane when it hit's that wall will wake it up if it's a lack of fuel problem.


OT a little ---
An ex dealer mechanic told me they have a problem with timing chains stretching (poor oiling?)
I doubt that's the problem in this case (a stretched chain seldom loses power unless it jumps) -- but wondering if anyone else has heard the same thing?
-----

In this case, my money is on the exhaust.
 

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[ QUOTE ]
A shot of propane when it hit's that wall will wake it up if it's a lack of fuel problem.

OT a little ---
An ex dealer mechanic told me they have a problem with timing chains stretching (poor oiling?)
I doubt that's the problem in this case (a stretched chain seldom loses power unless it jumps) -- but wondering if anyone else has heard the same thing?
-----

In this case, my money is on the exhaust.

[/ QUOTE ]

I know that the 4.0/2.4 sheds Fe (iron) at a much higher rate then most engines in used oil analysis. It's been speculated that it's from the timing chain/valve train. Heavier oils tend to reduce it.
 

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i have the same problem ,( sort of )98 tj 4.0 5 spd 49000 mi
upon initial start up ,it wont go over 2500 rpm in 1st, till
it acts like it hits a wall, shift to second 2500 rpm ..wall..shift to 3rd 1500 rpm ...wall.. feels like no fuel or plugged exhaust ..but i can push in on clutch and rev it high ,like 3000 rpm no problems ,then it comes out of it after 5-10
minutes if driving ,i replaced crank pos sensor and throttle pos sensor with no change , i dropped mine off at my independant mechanic last night he's going to put his genysis on it and see what it shows,my fuel mileage went to heck also , i dont mean to hijack your thread but it sounds like we have the same symptoms i'll let you know what it took to fix mine when he finds something
 

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Before throwing expensive parts at it -

Usually when it's a lack of fuel, pump, filter etc., it'll backfire when you try to push it beyond the point where t goes lean. It's not a hard and fast rule, but "usually."
The propane trick will very quickly tell you if you are on the right track - or way off base.

The description of "hitting a wall" sounds more like restricted exhaust.
Have someove rev it up to that point while you listen behind it - often you can hear a whistle or whooshing sound behind it if the exhaust is plugged. Compare it to another car's sound.

Then to verify that, loosen the headpipe - open the gap about an inch or so - take it for a quick drive - your neighbors will love it!

If it's better, that proves it - could be the cat, or muffler.

A symptom like that at the wrong shop will get very expensive before they get close to the problem - if ever.
 

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ok guys i got mine back from the shop ,been driving for a week ( wanted to make sure it was fixed ), it ended up being upstream O2 sensor , its a heated sensor and when it would go into closed loop it would lean it out, i have had no problems since, hope this helps someone else sometime.
 
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