Clogged Muffler from Cat inwards
 

Is it typical for a Cat that has gone bad with rattling inside to clog the Muffler? Just wondering if changing the Cat will fix the No power problem or if the muffler has become clogged with whatever broke down from the Cat

If you think you might have a plugged cat or exhaust, try removing a oxygen sensor and start it up. If you cat is plugged, you should see an immediate difference (not perfect, but huge) in power and response. since a 7/8 "test" hole is adequate.

make sure its a sensor before the cat, not after.

You could pull the post cat o2 and see if you have anymore power. I would think that most of the junk from the bad cat stays there.

It's not unusual for the muffler to get clogged with broken debris from the cat. It just depends on how badly the cat's insides have broken up.

In my experience:yes. If the medium breaks up into fine enough pieces,it will clog the muffler,but if you have to swap the cat do the whole system for peace of mind,they are cheap enough! I did my muffler and tailpipe today and took me just about an hour,I used stainless hardware and anti seize the last time, I had the system apart and I had the old system off in 10 minutes!

Conclusion: I drilled holes in the front of that Cat knowing I will have to cut out the cat and replace it anyway. Power got better. But that raised my question.. Hmm, The muffler might still be clogged from the Cat . Knowing the Cat was toast. I decided to do a Cat-ectamy. I cut off the Shield and I cut about 60% of the bottom off the Cat. Cut three sides and just scored the 4th so I can open it. Most of the inwards were attached but just broken lose from the Metal shell. An Impact Hammer easily broke the Inwards out and in no time it was an empty shell. Welded it closed, crossed my fingers and took it for a ride, Runs great. So the Muffler is still open. At least we are back on the road until I can do the job correctly. I put a 18mm Spark plug Non Fouler on the 'After Cat' O2 sensor and haven't put enough miles on it to see if it pops a Code.