98 Honda Civic DX 220,00mi

Car threw P0420 code weeks ago. I ordered a new dorman exhaust manifold/cat combo, and denso upstream and downstream o2 sensors. Install went without a hitch(old manifold was cracked) Gasket connecting cat to exhaust looked to be in good condition so that is the only orginal part. The issue came up around 150 new miles on manifold/cat and both o2 sensors. I was driving 50mph and attempted to pass a vehicle, when I accelerated, about 5 seconds in, I heard a loud backfire and saw what I can only describe as like stuffing from a couch, foam, or packing peanuts. It was grey in color. The wind blew the material off the road as I looked in the rear view mirror. Car running very fine. Not 100% knowing it was a backfire or I just took out some bird that flew in front, it happened the next day after about another 50-75 miles. This time it was at slower speeds of 30mph and the same "material" came out. I feel I am certain it wasn't smoke. Without knowing what is really inside a catalytic converter, I assumed it was the filter "blowing out" until I later learned the filter is made of ceramic. Car runs great and have put 300 miles without throwing any codes. Anything??

 

Is the muffler on the car stock? Does the car sound louder than it used to?

 

Yes stock muffler. No car does not seem louder.

 

Uh...maybe it was packing material stuffed inside the new cat? if the car isn't louder, and still feels the same, and the CEL isn't on, I wouldn't worry about it.

If it happens again, pull over and find that "stuff" to figure out exactly what it is.

 

Any of your friends enjoy a good practical joke?

 

Betting money its material from cat. Inside of cat looks like a metal honeycomb.

 

Yeah thats what I'm starting to think. I found the following.

http://www.easterncatalytic.com/educ...ture-problems/

Anyone got any ideas on the backfiring?? Could me leaving the original o ring gasket between the cat and exhaust pipe be a related issue??

 

probably not. any cel's at all? you could have a defective converter. the backfiring could be due to the cat.

 

If OP's car had bona fide backfires, then the focus should be on the engine, not the cat.

 

true. lets not forget converters dont just die, engine problems kill them. op- do you burn oil, etc?

 

I was going to mention something about Solbrothers backfiring and shooting objects out of his tailpipe, but I forgot this isnt GDD, carry on