MuffZ28

My ses light went on and Auto-Zone scanned it at a code: P0420, Catalyst System Efficiency Below Threshold, left bank. I've recently rteplaced the O2 sens. They said it might sens or a bad/plugged cat. I live in Ok with no smog. Can I replace cat w/ pipe? Would a new cat be better for sensor reasons? Just married w/ newborn. Looking fior cheapest way out with-out doing harm.

JBirdSS

I had the same exact senario in my 96SS and here is my suggestion for you. Look for replacement cats for your car and purchase both sides. Try these guys http://www.stranoparts.com/index.php
Have the cats installed at a muffler shop and make sure you leave with no leaks anywhere in your exhaust system. Look at the old cats they remove and see if they are clogged....I'm guessing they will be for sure. Your options for the long run are as follows. Change the after cat O2 sensors if you get an additional code, and make sure your ignition system if working to spec. and you have no misses. Be suspicious of running rich and check your milage very accurately. I just drove from San Luis Obispo to Lancaster a distance of 230 miles in mostly 6th gear trying to get good milage and got 26.2 MPG and you can look at my sig to see how my car is set up. If you are above 20 MPG I would guess your airfuel ratio is within limits.
I don't recommend running your car without cats if you want to maintain the ability to diagnose future problems with a shops assistance and don't have scanning capabilities of your own.

MuffZ28

Are there 3 cats on my car or only one? It looks like there's mini-cats on the manifolds for each side. Then dump into a Y into cat , over rear, then sinngle in/out muff.
xxx= cat
x= poss cat?
----x--\
\
----xxx---------m
/ u
/ f
---x--/ f-----

EviLBoX

You've got 2 cats. The driver side cat is connected directly to the exhaust manifold while the passenger side cat is under the passenger seat.