I have a question about the o2. What does it do exactly? my understanding is that it monitors the o2 in the exhaust and adjusts the air fuel mixture? is that correct?

The answer is in the name; An oxygen sensor measures the amount of unburned oxygen in the exhaust system left after combustion in the engines cylinders. Based on the amount of Oxygen present, the sensor genrates a voltage which is read by the engine's fuel management system. Too much residual O2 in the exhaust, and the Jeep's computer releases more fuel for the next combustion cycle; too little O2, and the opposite happens. This balancing act happens many times every second to maintain the optimal fuel to air ratio of 14.7
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Big Jim's correct! The most common Zirconia O2 sensor acts as a battery of sorts, it creates a low voltage based on the difference between the amount of the oxygen in the exhaust vs. the amount in the atmoshpere. More O2 in the exhaust, less voltage will be produced. Less oxygen, more voltage will be produced. Lean running or a misfire results in more O2 in the exhaust. Rich running results in less O2.

As Jim stated, the PCM reads the voltage signal from the O2 and it reacts by adjusting the pulsewidth to compensate.

The designers could make the system adjust to a steady 14.7 air/fuel point, but they choses to vary the pulse slightly richer then leaner than needed to allow more fuel then more O2 into the cat converter to boost it's efficiency. This is the O2 sensor "Switching point" This "Cat food" alows the cat-converter to maintain the required temperatures (the fuel part) and gives the cat added O2 (the oxygen part) to allow the catalysing action to occur.

Marty I have been told that some of the manufactors go below 14:1 for a length of time and then jump the mixture over 15:1 to cool the overheated valves.. The results, I've been told, is a little more mpg. So there is always a fluctuation in the pulsewidth. It seems overheating is the reason to not go below 14:1 for any length of time.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Other way round BJ 15:1 (lean) heats the valves. Then they go rich (13.5ish:1) to cool.

HAd my head under my wing again..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

ok so i am going to revert toa prev. post i had months ago about my jeep sputering, almost stalling...what ever you want to phrase it. last time i put some injection cleaner in the tank and it stopped. but now its back and cleaner not working, so i thought maybe some dry gas. nothing seemes to help. not at the same time of course, and i cant pin point the cause. so then i came up with the o2. Because i have an exhaust leak before the cat. so i was thinking that would it be possible that the leak is allowing too much oxygen in the exhaust thus giving the o2 a false reading making the engine run too rich making it flood out thus making it run rough or sputter. Any thoughts???

it is entirely possible that a leak in the pipe is sucking air into the system. Not all do but if air is entering then there would be a negative response from the computer. I am not so sure the results would be a richness that would cause sputtering and almost stalling.
What is the engine doing at the times this happens..Pulling a load such as a hill or lugging in a gear? Does down shifting help? Does it do this while ideling? Give us some help here.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

It happends at idle, driving, whenever. When driving, its like you take ur foot off the gas and it dies down, so i let off and then try to give it some gas to try and get it going again or back to normal. it lasts for a minute or so then its fine. sometimes i when i drive it its fine the whole time. at its worse its goes on for a mile or so. but i have noticed it does it more often when i stop and start to go. i've talked to some people some think its the injectors, or fuel filter, fuel pump, pressure rail. i dont know...kind of fustrating....

Have you replaced the fuel filter? Cap and Rotor? Plugs?
Does it throw a check engine code?

For those weird intermittent problems I always start a tune up if I know the engine has been sorta neglected. It usually doesn't fix the problem but you get two things out of it.
1. You just did the routine maintenance that should have been done.
2. You can inspect the other systems while in there.

It sounds like it could be a failing distributor bearing, plugged filter, ETC... Internet diagnostics is fun and useful <img src="/forums/images/graemlins/cheers.gif" alt="" />
If you have done a tune up recently, Check out the distributor shaft. If the bushing is failing, the extra clearance allows the magnetic pickup to change clearance giving it weird mis-fire characteristics when warm.
If the distributor feels tight, I bet it is some weird intermittent electrical problem in a weird unrelated system to all the ones most people say (isn't that helpful!).
Also... It could be a faulty TPS...
Or...
....
...
If youÆve tried everything... you could try an O2 sensor, but I doubt it would fix it. When you floor it, the jeep goes open loop and ignores the O2 sensor.