Catalyst 1/1 Efficiency Failure

I'm getting engine code P0420 "CATALYST 1/1 EFFICIENCY FAILURE " can anyone tell me what could be causing this? I was thinking I might need a new catalytic converter... the symptoms are lots of stuttering whenever I take off from a stand still to the point where the car won't even move until I floor it out of frustration.. gets even worse with AC on.. the car is a 2k base model. I replaced plugs an wires, helped a bit, but a week later it returned in full force. Any help would be greatly appreciated!

i got the same code... what was the problem?

i got the same code... what was the problem?It could be either your O2 sensor or a bad catalytic converter.

The computer is expecting a bigger difference between the upstream and downstream sensors. It's not seeing that, therefore it is presuming the cat is failing.

possible causes:
-intermittent condition
-visually inspect the cat converter
-exhaust leak
-engine mechanical condition
-aging o2 sensor
-cat converter

The computer on your car monitors the front and rear oxygen sensors for cataylist effiency. If the front sensor is switching fast and the rear is switching slow, the cat is working. If the rear sensor is switching just as fast as the front then the cat is not working.
You could have a bad cat. Or you could have another problem that is causing the sensors to act alike tricking the computer in to a PO420.
If you are having drivability issues also, that is my bet. You could have a vacuum leak causing the computer to add too much fuel trying to compensate for sensors showing lean. You could have an injector sticking open or closed causing a misfire. You could have an ignition problem or even a bad cylinder.
All of these will cause false readings and PO420. Or you could just have a bad cat. Check the basics first. They can save you time and money.