Sweet Reply! ^^^^^^^^
A couple of easy ways to tell if your Cat is bad is simple.
1) Smell, if you smell the exhaust coming out of the pipe and you get a burnt metal, burnt egg or even a burnt oil smell, it could be clogged up.
2) Sound, have someone drive your car on an open highway, or you do it, but have someone following in another car and have them place their car right where the exhaust is on your car. Then FLOOR the gas for a couple of seconds and see if there is a HISSING sound coming out of the tailpipe.
If you smell or hear any of the above, then your cat is definately bad.
If you DON'T smell or hear any of the above, then look at your 02 Sensors. Your car is old enough to need them.
Also, try putting a can of BERRYMAN B-12 Carburator/Injector Cleaner in your gas tank every oil change. It will clean from the gas tank to the tail pipe.
I've been using it for over 25 years.
When we bought our 04 Optima, it still had the 2006 Emissions test info. I had to get it inspected in 07 and before I took it down to get it inspected, I put (2) 16 oz cans of that in with a full tank of gas, and once I was down to about 1/4, I fill the tank and took in to get inspected.
Our emissions were almost non existant! They guy said our car posted #'s that nearly equalled that of hybrids!
I checked our NO2 and Hydrocarbons and the numbers were way below the 2006 inspection.
So try it. But remember, put 2 in the tank and fill w/ super unleaded and run the heck out of it. If the cat can be saved, this would do it.
Need Help? Let me know. I might be able to answer your question.