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.
I replaced all 3 cats and it feels the same as it did with the picture above.
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
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.
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.
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.
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?
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.
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.
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..
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.
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.
One thing I was thinking is that since the cat was clogged all the pressure that wasn't getting out damaged the valves? Could that be? That also goes back to the pressure which I'll be checking soon.
Old wives tale. EGT can/could go up but not to the point of damaging valves and seats. Besides you would be throwing more then a 432 code if that was the case.
An engine needs three things to run: fuel, air and spark. Checking the fuel pressure will eliminate that one, except for a clogged fuel injector or the computer screwing with fuel delivery. Air is easy as long as you have a clean filter and clean throttle body (though a dirty throttle body usually has more effect at idle than when you are at higher rpm). The computer can think there is an air problem if you have a faulty IAT or MAP sensor, or if you have a vacuum leak. Spark is the tough one since with DIS that is entirely computer controlled, and outside of checking your plugs there is not much you can do.
I am going to say it is probably not an O2 sensor issue. Before the sensors get up to operating temperature the computer doesn't listen to them anyway and runs open loop off of preset tables. If the vehicle behaves the same when cold it is probably not a sensor.
I would guess it is either fuel delivery problem, clog somewhere in the exhaust, or maybe a vacuum leak.
One other thing the OP could try, you could try to reset the computer to clear out any "bad" behavior that it has learned. It will default back to factory programming and begin relearning based on current conditions and your driving style. Probably not going to fix it, but its worth a shot.
OP: Did you replace the muffler as well? When the cat disintegrated on my last TJ the ceramic material blew back into and clogged the muffler. If you haven't replaced the muffler do yourself a favor and have someone rev the engine a bit while you hold you hand at the end of the exhaust pipe. If you don't feel a significant increase in flow at higher rpm's my guess is you need to replace the muffler or figure out a way to get the debris out. HTH :thumbsup:
To the OP, before doing anything disconnect the 02 sensors and see how it runs after that , then if still the same,pull the plugs inspect them, do a compression check.
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