What are the symptoms of a bad cat? What would I see on my scanner in terms of O2 readings and Injector Pulses?

My primary O2 sensors on each side look good fluctuating between 100 and 900, but the post cat sensors are behaving strange. One of them stays high (in the 800's) the other stays low around 80. (I recall that I read that the post cat 02's aren't suppose to fluctuate much, but I dont remember if they should read high, or low?

Could a bad cat cause the odd 02 reading, which would then in turn cause the car to run rich? One side of the engine, as shown by the injector pulse width is running rich.

 

One way to tell if its bad is if its glowing red (clogged).

 

Nope, not glowing. In fact, the one I think is bad is actually cooler (as measured with an infrared thermometer) than the one on the "good" side.

 

What are symptoms of a bad Cat?

They pee on the floor and claw up the furniture.

 

A CLOGGED Cat will often cause a pronounced hissing sound on acceleration as the excess pressure finds it's way out; perhaps at the ball couple or a weak seam.

 

Hit it with the handle end of a screw driver, if things rattle inside, it is probably bad.

 

Thanks for the replys guys, but what I'm looking for is to know how the Post Cat 02 sensor, and the injector pulses might act differently when the cat is bad.

 

testing for a bad cat through the post 02s is not a good idea. neither is pulse width. there are many other better tests to run for checking if your cat is bad. if your cat is bad in the sense that it is not filtering the exhaust like it should, then your pcm should store a trouble code for this. if your cat is bad in the sense that it is clogged, then the best thing to do is to take it to a local muffler shop and have them test the backpressure of the exhaust with a gauge. they can tell you right off if it is clogged. i've also found that the pre 02 sensors are way more useful in diagnosing a clogged cat. they stay more on the rich side due to the lack of release in the cat while driving. also your LT trims will be on the subtracting side while normal driving. for example- 115 and below. so if you're looking for something on your data scan to help you, i recommend monitoring the LT trims above all else [while driving]. they should be 128 +/- 6 at all times except for WOT. if 1 side is below 120, suspect that bank for a clogged cat.