HI there well i have a 94 ram 4x4 5.2. I use this truck for mudding races only and its in mexico well i live in a border town. Im going to remove the cat and was thinking if the O2 sensor had to be moved or if i could just remove it. I did the same thing to my jeep when i put the headers on and removed the sensor and well i didnt notice a difference.

 

Will probably affect how smooth it runs a little bit, and gas milage but if your doing mud runs I'm sure MPG isn;t really a concern.

You can buy O2 Sims. www.thefastman.com has them

 

Dont remove the cat, just hollow it out and put it back in if you want to remove it (I suggest not doing either and just going with a high flow cat). Yes you need he O2 sensor thats after the cat, the engine uses it to either lean or richen the fuel.. Without it you will get a really really rich fuel mixture, burn more gas than needed, and probably never get the engine properly running again.

 

The PCM may try to make compensations by running rich or lean, depending on what it thinks the problem is. It will throw a code too, but sounds like for the use you stated, you probably won't care if the check engine light is on. O2 sim would probably be your best option.

 

I think most of the time it dumps fuel (runs richer than rich). The after, or downstream 02 sensor is for diagnostic purposes only. It will just throw codes, and doesn't have anything to do with the a/f ratio. The before, upstream sensor controls the a/f in closed loop operation. You will make more power if you can keep it there. If you remove it definately remove the cat, as it will go in short order anyway with no 02 sensor.

 

Removing the downstream or post-cat sensor WILL cause a rich condition. If you have to remove the cat, replace the sensor with an o2 sim from the link that Socha provided.

Your truck must have California emissions on it....because otherwise a 94 wouldn't have a post cat sensor.