So I've been having issues lately with my '96 xj. The exhaust smells real bad, it feels down on power, and it gets around 10-12 mpg (granted I am running 33"s). I suspect the catalytic converter is probably plugged due to problems I had with my O2 sensors about a week ago. My friends step dad told me I should just smash all the honeycomb ceramic stuff out of it, and put it back in place. I just don't think that's a good idea though. Like, will it improve the power issue, the smell, and the mpg? Or nah? Idk any suggestions would be appreciated, thanks!

 

There are many threads with this same question on here. 1) it is a bad idea to discuss this on the forum because it is illegal 2) a new converter is not terribly expensive and much cheaper than the fines you could incur for knowingly altering the converter or removing it.

 

Removing the cat might improve power, I saw might because normally aspirated motors need some back pressure in the exhaust to help it flow so the cat helps with that. As far as smell, no that will get worse with no cat. Bad mpg usually happens from bad O2 sensors or vacuum leaks, does your Jeep run rough? feel like its misfiring or hunting idle?

 

There is still an active recall on 1996 xj c/c's. Check here for info.

http://recalls.mopar.com/

 

Really not much benefit in power when removing a catalytic converter. We are talking between 1-5hp here. Better to replace it and not worry about smog issues for inspection depending on where you live I guess.

 

Not to mention the smell. I have a corvette with no cats (removed them when longtube headers were installed) and I smell like a lawn mower after driving with the windows down.

 

You need to replace the cat and sensor in order for the engine to run properly and to correct the fuel mix by the computer. Never a good idea with a low performance engine like the 4.0 to ever remove one causes to many problems.

 

Not to mention IIRC the cat is a spark arrester as well.

 

And the best part is removing it is illegal. And debating it is strictly against forum rules which I'm suprised no one has mentioned yet.

 

Cliffy mentioned the bad boy aspect of removing/dicking with a Cat.

 

Woops missed that sorry.

 

I know some guys that take them off their trucks/jeeps, and when you drive behind them you'll about pass out from the smell. Performancecurve.com sells them for cheap; they even sell a "high-flow" catalytic converter.

I'll be honest, I had mine off for like a month and didn't care for it. I couldn't tell any difference in performance, and it was just too loud for me since I use my xj as a hunting vehicle.

So, just replace it and stay legal

 

Some of the mom and pop exhaust shops can weld you in a new one under 100 bucks if you shop around.

 

No inspections where I live but when I took mine in to replace the exhaust, someone had removed the converter so, by law, they had to put one back on.

 

You make the most important point, The O2 sensor reading is critical for proper performance and It is dependent on the Cat to run at these proper temps.