Does anyone know the expected live readouts of the o2 sensors while idling? I wonder if my ECU even realizes an o2 sensor is connected. I don't have any check engine lights though. Nothing would lead me to think it's an exhaust related issue. I guess if computer isn't getting right data then maybe? But you're right, I originally thought my exhaust was stock, but that seems not to be the case...
4.0 on 33's struggles to go past 60 mph
- Thread starter Sensei
- Start date
Does anyone know the expected live readouts of the o2 sensors while idling? I wonder if my ECU even realizes an o2 sensor is connected. I don't have any check engine lights though. Nothing would lead me to think it's an exhaust related issue. I guess if computer isn't getting right data then maybe? But you're right, I originally thought my exhaust was stock, but that seems not to be the case...
You’re 3rd cat is probably stopped up,that one is easy to unbolt and look into it,your not getting a reading because there are no cats
Is 3rd cat the one you can see in my video? Next to the transmission inside the skid pan?
Looks like I got 1... Where would they even plug into? I haven't noticed any empty connectors or anything like that....
Hmm based off this image for my model year service manual, it seems like my setup is in fact stock. Only shows one o2 sensor, those other 2 things by the arrow labeled 4 are bolts. Not o2 sensors like I was originally thinking. So it would seem my setup is in fact stock. And I only have 1 o2 sensor from the factory. That's my conclusion so far.. Also I believe this exhaust was used for a later in the year built 2000 jeep tj. Other years, or 2000's built in january (earlier in the year) use a different system.
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Heres a diagram of early model year 2000 exhaust. Label 7 states two additional o2 sensor on the manifold, prior to mini cats, were only present on California models.
But then again, this diagram from the same manual shows that I should atleast have mini cats, as well as it having some unlabeled drawings which I suspect might be where o2 sensors would usually go. But it's unlabeled so I have no idea. And there seems to be discrepancy between the two diagrams for the same late-model year vehicle. Pretty confusing xD
Oh more details about the mini cats, just had to read a bit. Seems like california only had mini cats. All others (i.e Federal?) models did not. Taken from the manual below,
The basic exhaust system consists of exhaust manifold(s), exhaust pipe with oxygen sensors, catalytic converter(s), heat shield(s), muffler and tailpipe The 2.5L and 4.0L Federal Emissions vheicles use a single catalytic converter, while the California models use additional mini catalytic converters inline with the exhaust pipe below the exhaust manifolds. CATALYTIC CONVERTER DESCRIPTION California emissions vehicles incorporate two mini catalytic converters as well as the under floor catalytic converter, into the exhaust system. These catalytic converters are made of stainless steel designed to operate at extremely high temperatures. Federal vehicles use a single under floor catalytic converter only (Fig. 1) (Fig. 2) (Fig. 3).
The basic exhaust system consists of exhaust manifold(s), exhaust pipe with oxygen sensors, catalytic converter(s), heat shield(s), muffler and tailpipe The 2.5L and 4.0L Federal Emissions vheicles use a single catalytic converter, while the California models use additional mini catalytic converters inline with the exhaust pipe below the exhaust manifolds. CATALYTIC CONVERTER DESCRIPTION California emissions vehicles incorporate two mini catalytic converters as well as the under floor catalytic converter, into the exhaust system. These catalytic converters are made of stainless steel designed to operate at extremely high temperatures. Federal vehicles use a single under floor catalytic converter only (Fig. 1) (Fig. 2) (Fig. 3).
If your TJ is a 2000 then that might be your stock exhaust, I think that 2000 was a weird year as far as new and old exhaust setups from the factory.
I was thinking yours was a 2002 for some reason, must have been remembering the wrong thread, that's my bad.
If the test you did earlier had your test rig upstream of the single big cat, then it seems like it may not be clogged. I'd double check it with the other gauge when it shows up just to be sure though.
If it's not clogged, then I'm not really sure what else your problem might be if it's not throwing any codes. Definitely check for codes with a scan tool if you haven't already, just in case your check engine light bulb might be out or something.
I was thinking yours was a 2002 for some reason, must have been remembering the wrong thread, that's my bad.
If the test you did earlier had your test rig upstream of the single big cat, then it seems like it may not be clogged. I'd double check it with the other gauge when it shows up just to be sure though.
If it's not clogged, then I'm not really sure what else your problem might be if it's not throwing any codes. Definitely check for codes with a scan tool if you haven't already, just in case your check engine light bulb might be out or something.
Yes I did test upstream of the one and only cat I have. In the only o2 sensor hole I have (I believe). Will test again when that new gauge comes in. Also no codes when using my scanner. Wish my jeep drove apeshit like yours. I really gotta press this thing to keep it in the 60s. Really frustrating.
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I did find a second o2 sensor, immediately after the cat. So my common sense tells me that the computer is essentially measuring the “effectiveness” of my cat? I don’t really understand why I’d need an o2 sensor right before and then right after otherwise, but I’m no car engineer.
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Im about 95% confident now that I have a stock exhaust setup upon further research and investigation. Im also fairly confident that my cat is not plugged, although I have to double confirm with a proper tool to test back pressure later this week. So any other ideas why my jeep is struggling to go past the 60's? I'm thinking I should test fuel pressure next...
You could loosen the pipe and drive it. It will be loud but you will know. Check fuel pressure and run a check for codes
That cat completely unbolts,take it off and look you will know if it is plugged,
Ill unbolt the cat tomorrow to test, but then Ill effectively be losing my downstream o2 sensor reading. Will test the effect regardless and report what happens. If no progress, will test fuel pressure next. Anyone got a writeup or video for testing fuel pressure at the rail?
Down stream o2 only looks a cat efficiency to see how well the cat is functioning it will have no affect on vehicle operation. If the cat is empty the contents could plug the muffler.