Catalytic converter finally died on my XJ & I thought I'd just remove it completely. Mechanic advised against it saying it would screw up the computer... not sure if he was just trying to sell me a catalytic conv or it was true. Anybody have experience w/ this? Thanks for any advice!
My bro's '88 MJ has the stock cat.conv. on it. They don't really ever die, they just have no active metals in them to filter out the bad carbon compounds that supposedly destroy the ozone. You computer has nothing to do with anything from the exhaust on back from the engine. Your computer doesn't know jack about what passes through there. Tell your mechanic that your computer doesn't care about the ozone and would rather save his driver $175 to not have himself replaced.
Some mechanics try to sell you it to make money, but some are worried that you are an EPA guy trying to get the mechanics in trouble. The dude I went to twice to put on the exhaust just needs the wink and a smile and he leaves what has no holes on the truck.
Not sure what year your XJ is but on the newer models the cat has an o2 sensor after it. This tells the computer how to adjust itself based on the amount of pollutants leaving the cat. If your state has any kind of emmisions inspections you will automatically fail with no cat in place. The cat can also be damaged from the engine running rich or excessive oil consumption. They can even be damaged from a large impact (like hitting rocks on the trail) so they aren't totally indestructible.