First post. I did some searching around, but I don't really know how to word this.

1997 Cherokee Sport 4.0

Okay, so I don't know too much about all these sensors. But I'm fairly certain that I just completely murdered my downstream o2 censor (or whatever censor it is that attaches to your catalytic converter).

I went underneath my jeep after some light wheeling a few days ago, and the area where this sensor was was caked in mud. So I brushed the mud off, to find a small hole. Now, from what I have read, older converters will actually have a small hole so oxygen can flow into the sensor. However, this also leaves room for mud/water/salt etc.. to get into it. So I figured I would wrench off the sensor, clean it off with some electrical cleaner (please don't bash me if I messed up right there), and throw it back together. Well, in my attempt to wrench it off, I REALLY wrenched it off. Now the sensor is hanging onto the converter by a thread of metal and it runs A LOT louder.

In short, what do I do about this?

Sounds like you need to buy a new O2 sensor, NGK is the preferred brand for most people.

I don't think the sensor itself is damaged. I believe the metal that held it in place is damaged.

I believe a muffler shop could weld in a new fitting. Someone else jump in if you know a driveway fix, but I think if you knocked off the fitting it needs welding to repair.

If the threads in the cat are shot, I would take it to a mechanic or exhaust shop and see what they can do for you. Its its jacked up, you may need a new cat. To get O2 sensors out, I usually spray penetrant on the threads when the exhaust is hot. The usually come right out. Apply nickel anti-seize on reassembly. Nickel is high temp and the only suitable anti-seize for exhaust. The regular and copper can't take exhaust temperatures.

Here's a picture for reference.

Thanks for the help guys.

Following up on the post.

Problem was fixed for about $5 at home.

I welded a patch onto the original hole where the the sensor was, and added a new fitting onto the actual exhaust - right on the small pipe that runs between the converter and the muffler. Since the downstream sensor is after the converter, so long as it's still AFTER the converter, it shouldn't make a difference.

Oh, and the sensor was pretty much fused with the threading on the converter. I had to cut into the converter metal that was stuck on the sensor. Pretty sure I mangled the insides of the sensor, but still better than having to buy a new CAT.