02 sensor issue

Hello everyone,
My name is Albert a new member to the forum.
I'm a 20 y/o from Curacao and my Jeep is an XJ model from 1998 with 196K miles.

I've been having problems with my o2 sensor since I bought it.
We replaced the muffler (old one was rotten) and the shop took out my cat
without telling us.

Even with the cat out we still have to replace the sensor every 2 weeks.
We tried addressing the issue by plugging out the sensor but it has worsen my mpg alot.
My mpg is now 8 to 9

I would love to build my XJ but I don't want to do it knowing my Jeep isn't 100%

What I would like to know is..
How do I fix this properly ?

Regards,
Albert Jr.

Forgot to add
4.0 i6 engine
4wd
Chryco. 8.25 rear
Dana 30 front
Automatic
Don't know which transfer case/diff.

Well to start with if you're 100% sure you had a CAT before the shop worked on it then I would return and demand they replace it if you think they stole it. After that is taken care of then you can focus on the O2 sensor. My guess is there is actually nothing wrong with it, and it's actually dong it's job (by indicating there is something wrong with the CAT... like missing)!!!

scoobyxj said:

Well to start with if you're 100% sure you had a CAT before the shop worked on it then I would return and demand they replace it if you think they stole it. After that is taken care of then you can focus on the O2 sensor. My guess is there is actually nothing wrong with it, and it's actually dong it's job (by indicating there is something wrong with the CAT... like missing)!!!

Click to expand...

I'll go check that out.. thanks.

I'm saying this just in case.
The issue that I'm really getting is that it messes up my shifting.
This is why we took out the plug.

Sigh*
Turns out my uncle was the one who asked to get rid of the cat.
He did it as a surprise for me (as a gift).. he also paid for the muffler.

I can't get mad at my uncle..

What should I do now ?