cat is bad?

Joined
Jun 20, 2005
Messages
657
Location
Northern Colorado
How do you know if the cat is bad (insert bad joke here ____). Now it just passed smog without a problem, but I am about to replace the exhaust from the cat back and figured that this may be the perfect moment to replace it if it was bad.

Any help would be great.
 

Dunbar

SILVER Star
Joined
Jan 29, 2004
Messages
368
I asked the same thing yesterday when I had my exhaust rebuilt at the muffler shop. They said you have to look through it to see if you can see light. I kept both of my cats, FJ62, and the Y pipe but have not removed them from the Y pipe to look through them. They are original and have ~235k miles.

I went with 2.25" pipe from the manifolds to a new high flow dual inlet single outlet cat and 2.5" from it to the new flowmaster and out the back. Big improvement over the stock pipes as far as performance, easily made up the difference of going to 33"s from 31 inch tires. And, I eliminated the pipe going under the frame rail. Cost me $575 and $100 for the cat from Summit. I should have bought the flowmaster from summit too as they charged me $140 for it and I got the last one from summit for half that.

Dunbar
 
Joined
Apr 15, 2004
Messages
2,865
Location
Larkspur, CO
Take the skid plate off & run the truck to full operating temperature. The temp at the outlet of the cat should be noticeably higher than that at the inlet, & the cat itself should also be hotter than the header pipe (it's supposed to be burning HC). A laser thermometer that reads up to 1000 degrees F is real helpful.

You can't see through the cat - it's the "pellet" type, not the honeycomb.
 
Joined
Feb 14, 2005
Messages
471
Location
Tucson
Cat technology has improved so much in the last 20 years that even if it is functioning perfectly your ancient Cat should still be considered "bad". I would highly suggest having the dual cat setup replaced with a single cat with a 2.25 or 2.5 exhaust. Any half way decent exhaust shop should easily be able to make the required pipe. WHile your down there you may want to make sure your O2 sensors are working (62).
 
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