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Unread 11-05-2013, 04:30 PM   #1
Colorad0TJ
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4.0 is super sluggish

I also posted this in the general tech forum because I need answers!!

I recently bought a 2003 TJ. When I bought it I didn't know that it was severely underpowered until I drove my friends TJ. It has 33's with 4.56 gearing. It had been throwing a P0432 code so I dropped the cat's and there was one that was dislodged and had fallen down. (Pic below) I thought this would fix the problem of it being slow due to the clogged cat, however after replacing this it still has no power. What I mean by no power is that once I hit 2000 rpms there is no more acceleration no matter how hard I push the gas so I always have to shift at 2000 rpms. Does anyone know why this could be? I can't even keep up with guys who have 35's and 3.73s in the mountains.



image-2598853481.jpg

I replaced all 3 cats and it feels the same as it did with the picture above.

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Unread 11-05-2013, 05:03 PM   #2
Moezer
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check your spark plugs you might have the wrong ones, also change your oil another thing is what type of gas are you running? 87? 89? 91? if your running higher octane then that can be the problem.... you will get unburned gas going threw the cats causing them to fail
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Unread 11-05-2013, 05:37 PM   #3
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Change the O2 sensors
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Unread 11-05-2013, 05:48 PM   #4
Colorad0TJ
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Quote:
Originally Posted by afusco1222
Change the O2 sensors
Even if they aren't throwing any codes would they still affect the performance?
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Unread 11-05-2013, 05:51 PM   #5
afusco1222
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Yeah it happens pretty frequently. The clogged cat probably affected their performance. It's either that or the crank position sensor and both are fairly cheap. I would start with replacing both upstream O2 sensors seeing that the downstream O2 sensors really don't do anything.
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Unread 11-05-2013, 06:42 PM   #6
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You mentioned replacing the cats in another thread, are you certain the main catalytic converter that sits near the transmission was replaced too? A clogged main catalytic converter will produce that symptom.
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Unread 11-05-2013, 06:50 PM   #7
jsawduste
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Originally Posted by Moezer View Post
check your spark plugs you might have the wrong ones, also change your oil another thing is what type of gas are you running? 87? 89? 91? if your running higher octane then that can be the problem.... you will get unburned gas going threw the cats causing them to fail
Wow just wow on that response...........

To the OP, start with the fundamentals. Simply throwing parts at it is not the answer. Assuming you have no hard or soft codes stored in the ECM still. Compression check would the first thing on the list. From there would be fuel pressure.

The P0432 code would be for the cylinders 4, 5 and 6 (Bank 2) but even with that code the ECM would stay in open loop and not restrict your power levels to what you are saying.

Are the plugs, wires, rotor and cap reasonably fresh ? How about the fuel and air filters ? A check of the vacuum lines would be in order to make sure you have no leaks. A leaking exhaust manifold would induce a false O2 signal but not as bad as you are describing. No flattened exhaust pipe ?

If the power is as bad as your saying the problem should be pretty obvious. It runs so the crank sensor is providing a signal.

Start with the compression test and go from there.
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Unread 11-05-2013, 06:54 PM   #8
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I'm not going to pretend to have an answer, but I'm curious. How's your mileage? did you look at the plugs? How about the air filter? Does the vehicle look like it's been well maintained or does it look like someone bought it new and did nothing more than put gas in it?
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Unread 11-05-2013, 09:08 PM   #9
Colorad0TJ
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Quote:
Originally Posted by jsawduste
Start with the compression test and go from there.
If it is the compression, what are the symptoms and how does one go about fixing that?
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Unread 11-05-2013, 10:10 PM   #10
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Originally Posted by Colorad0TJ View Post
If it is the compression, what are the symptoms and how does one go about fixing that?
What I mean by no power is that once I hit 2000 rpms there is no more acceleration no matter how hard I push the gas so I always have to shift at 2000 rpms. I can't even keep up with guys who have 35's and 3.73s in the mountains.

Head gasket leak, valve leak, broken piston think internal.
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Unread 11-05-2013, 10:28 PM   #11
Colorad0TJ
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Quote:
Originally Posted by jsawduste
What I mean by no power is that once I hit 2000 rpms there is no more acceleration no matter how hard I push the gas so I always have to shift at 2000 rpms. I can't even keep up with guys who have 35's and 3.73s in the mountains. Head gasket leak, valve leak, broken piston think internal.
Okay, I'll check the compression. Thanks for the help. I'll post up what I find
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Unread 11-06-2013, 05:37 AM   #12
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Okay, I'll check the compression. Thanks for the help. I'll post up what I find
Please do. When you pull the plugs observe the business end and note there condition. Such as cracked insulators, oiliness, insulator color, balls of aluminum and comparisons between cylinders etc..
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Unread 11-06-2013, 05:43 AM   #13
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Are you sure parts of the cats aren't caught further down in the exhaust?

I disagree with replacing O2 sensors, crank sensor, or spark plugs. Far too expensive, and there's no reason to think any one of those things are bad at this point. If there is no difference in performance when you unplug O2 sensors, they they aren't the problem. A crank sensor isn't going to give you problems at only 2,000 rpm. Spark plugs can easily be evaluated, but again, they aren't going to limit you to 2,000 rpm.

Does it run ok up to 2,000 rpm?
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Unread 11-06-2013, 08:22 AM   #14
jsawduste
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Are you sure parts of the cats aren't caught further down in the exhaust?

I disagree with replacing O2 sensors, crank sensor, or spark plugs. Far too expensive, and there's no reason to think any one of those things are bad at this point. If there is no difference in performance when you unplug O2 sensors, they they aren't the problem. A crank sensor isn't going to give you problems at only 2,000 rpm. Spark plugs can easily be evaluated, but again, they aren't going to limit you to 2,000 rpm.

Does it run ok up to 2,000 rpm?
All very true statements.
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Unread 11-06-2013, 08:33 AM   #15
Colorad0TJ
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Originally Posted by bobjp
Are you sure parts of the cats aren't caught further down in the exhaust? I disagree with replacing O2 sensors, crank sensor, or spark plugs. Far too expensive, and there's no reason to think any one of those things are bad at this point. If there is no difference in performance when you unplug O2 sensors, they they aren't the problem. A crank sensor isn't going to give you problems at only 2,000 rpm. Spark plugs can easily be evaluated, but again, they aren't going to limit you to 2,000 rpm. Does it run ok up to 2,000 rpm?
I replaced all 3 cats so if there was a part of the cat stuck I would have removed it because I replaced the whole assembly. The car seems to drive fine before 2000 rpms but with my 4.56 gearing it doesn't take much to get it to 2000 rpms so I can't tell too much.
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