Quote Originally Posted by green91
I'd say your car has a very lax monitoring strategy for the CAT then. They do gradually go bad over time. The CEL comes on when the catalytic converter's efficiency actually is less than a determined value in the computer. So they can be gradually going bad, but not set the CEL until its to a certain point.

Cat converters are usually a 2-trip logic detection code. Meaning it takes 2 complete drive cycles to run the monitor to check to see if the cat is good. Its possible yours on right on the borderline right now and at times just makes the mark and sometimes come up short. It probably won't hurt your car to drive with it like this, but it will get to a point where the CEL is constant.
i don't want to risk screwing anything up. i have another O2 sensor im gonna put in but im also gonna pull the cat off and check it out. it was a constant CEL when the fuel pressure was low, but after that it went away for several months almost like the o2 code i used to throw, the sensor was good but the ecu couldn't figure out what was going on. i for some reason think im about t have to spend $$ i dont have to keep the car on the road and not eat up the premium gas i have to run.