I'm trying to remember how to diagnose, with fairly good accuracy, a clogged cat. I know something is wrong, as my manifolds glow. I am going to replace my o2 sensors, as I have no idea when they were changed last, and look to be old visually. I just bought this car, so I'm still figuring stuff out on it, what's been done in the past to it, and what needs fixed. I'm pretty sure I have an exhaust leak on one of the banks, because I can hear it. I haven't looked really well yet to see if I have on 100%, but I've heard them before, so I'm pretty sure that's what it is. Both bank's manifolds are glowing. This is a 95, so it has one cat, dual o2's.

Anyways, thoughts and ideas are welcome. I'm wanting to say that a good way to tell if a cat is clogged is by measuring the temperature of the exhaust pipe before the cat and after the cat. If the temperature is significantly higher after the cat, that usually indicates a clogged cat. Right?

Thanks for any help you can give. Oh, a side note, the car runs really well. I know once I get the fueling figured out, and the mani's stop glowing, it should run a little stronger. It has zero misses, runs good, though it does get pretty bad gas mileage last time I checked it. I think the only mods it has is an aftermarket cat-back, some sort of MSD ignition box sitting external, with the rest of the ignition and fuel system being stock. Oh, has a CAI as well. Things I've done to fix problems so far, engine wise, is run cleaners through the fuel system (gas tank, injectors, and through a vac line). I've replaced the plugs and wires. (stock temp range plugs, stock type wires) I've cleaned the MAF, cleaned and slightly ported the TB. (port matched to the intake)

 

you could just cut the cat off

 

I personaly prefer gutting cats. Leave the housing in place, just in case the man wants to take a look under the car.

 

The exhaust will get really friggin hot and the car will run like *** (because the exhaust cannot escape).

Remove the cat, put an off road pipe in its place and take it for a test drive.

 

best way is to use a backpressure gauge before the cat, or do like i do... use a vacuum gauge off the intake manifold. low vacuum is a key sign! sporatic misfires across the cylinders, no power, sulfur or eggs smell from tailpipe... theres a bunch

and i prefer to weld in pipes or use an ORY... just a matter of opinion though

 

my 97 has the two cats. is the bigger one on the driver side made the same way as the second smaller one? je it seems like it would be diffacult to get the first one

 

easiest way to diagnose a clogged cat:
drop your I pipe, look inside with a flashlight. if the beehive is completely intact and doesnt move when you poke it, it is most likely fine. if its broken, sticking out, or loose, its clogged.
if its clogged, simply take a long screwdriver and a hammer, break it apart and start the car every few seconds to blow the crap out of it. then reattatch the I pipe and take her for a ride.

when mine was clogged the car would not rev past 4000 or 4500rpms, and felt like it had lost alot of power. sure enough, when i dropped the I pipe, pieces were sticking out and broken. gutted it, never ran better.

 

You could drive to Wendover and have your car die 30 miles away because your damn cat collapsed and be stuck out in the middle of nowhere for 6 hours while the tow truck comes. Thats how I found out. Just a suggestion.

 

LOL @ SCTA. No thanks.

Thanks for the information guys.