I note that some of us have had failed cats and was wondering if the car throws a check engine light on failure. I note that there's a sensor (oxygen?) entering the side of the cat and was thinking it might be monitoring the cat's health.

I have reason to believe that my cat has slagged as I'm hearing a really weird noise coming from the middle of the car when the car first moves after a stop (forwards or backward) and also, to a lesser extent, when revving the engine after a stop when out of gear (clutch in or out). In all cases, the sound only happens once and sounds like little pieces of something rolling around on a thin metal surface.

The car has also develoed a really foul exhaust smell. I've had a lot of older sports cars over the years, most all of them pre-emission and this smell tells me that it's very unlikely the cat is doing its job.

I would have the emissions tested in order to verify the cat failure, but a software bug in the state of Georgia's emissions testing computers won't allow RX8's to be tested (they have the car entered as 'two cylinder'.)

I'd like to hear anyone's experiences with a failed catalyitic converter.

Thanks,

- Eric H. in Marietta, GA

2004 RX8 6-speed - 1976 Alfa Romeo Spider

 

my catalyiti converter is also giving me some problem too.. when i try to gas my car its not smoot and it hesitates. And mazda told me i need a new one

 

some do and some dont. it is odd.

i think more than often they dont... but if you pull the cat and look in it, it is very obvious if it is bad..

beers

 

When mine went I didn't throw a cell until it was so backed up it wouldn't go over 6K RPM.
No smell on mine. No weird sound. Just no go.

 

The first week I had my car it threw a CEL. No symptoms when I took it in they replaced the Cat. I didn't get to see it to say if it was obvious but can imagine if it breaks apart it can be seen.

If a catalytic converter clogs is it possible to see the damage that has been done?

 

I'm used to O2 sensors sitting in front of the cat...Bosch L-Jet and Motronic designs where the downstream system is of no concern to the operation of the engine. Unless, of course, there's a blockage as 8is>enuff experienced.

Thanks, swoope, for at confirming that the guts can melt without a CEL. I'll pull it to confirm a meltdown if possible prior to taking it to the god-awful dealership here.

 

4 years,

Most of the cats I've seen can be visually inspected to some extent. They're like a screen door...lots of tiny squares or hexagons running the length. (Some really old ones were made up of a bunch of pellets -- this design is what caused 'car guys' to believe that catalytic converters hindered performance...they did.)

A partial failure would cause blockage with many of the chanels closed. A total failure would leave a shell with melted debris on the bottom. The slag can be a solid mass or in bits and pieces. I'm thinking I've got bits and pieces.

 

this is what it should look like..

beers

 

And here's MY previous cat - with NO CEL's showing.






Current cat is bad, too - I'll post up pics when I remove it.

 

note,

my cat is not stock..

and dmp. that is some clogged up stuff..

beers

 

It will only through a cel when the rear o2 sensor reading around the same voltage as the front.

 

Dmp is the material on top of the battery chunks of the honeycomb?



BTW thanks for the pics dmp and swoope.

 

i think i can answer for him. it is.. ugly isnt it...

beers

 

Yes it is.

I guess I didn't think the cat honeycomb material was as long as it is. No wonder they tend to fail.

 

4 years, I think I read somewhere that there are 2 sections of the cat. 3in section of honeycomb in front of the o2 sensor and a 7in section after it

 

OK, so if the forward part of the cat (the shorter section?) doesn't slag but the back half does, then it's unlikely to see a CEL?

I was under the car on Saturday surveying the situation and searching for a likely cause for the odd sounds I've been hearing (and verifying that a new starter was, in fact, installed and puting my spark plug wires right as the dealer failed to return a single one to the loom attached to the coil pack rack -- they did manage to tangle them up real nice, though). I vaguely recall seeing another sensor 'upwind' of the cat. So the differential thing makes sense.

Anyone notice a different tone to the exhaust when the cat failed?

 

that one did eventually throw a cel but was clearly failing for some time before doing so

 

Was there a bad smell? (Unburned fuel/exhaust gas) Did that big chunk make metalic rattling noises?

 

hey i got one..... what does it mean wen the "ring" around my 02 sensor glows red....... i think its only a "ring" cuz the heat shield. but yea n e one no wats goin on?????

 

The whole cat glows, the ring is the only piece you can see because of the heat shield.

S

 

I think your cat is bad - shouldn't glow like that unless it's backed-up, IMO.

 

Just took my 04 with 31k miles in for cel. Dealer replaced the cat. I was told the exit diameter was appx 1.5" as opposed to 2.5" it should be. I did not see the old cat but the car does seem livelier tho it never was obvious there was a problem.

 

How much does a replacement run?

 

Here in Canada, the piece is $1600, so I'm guessing "over $1000" in the US.

S

 

i just replaced the cat on mine. few points:
that rattle described in the original post is pieces of the cat guts sliding around.
cost of a stock unit is around 1100 (needless to say i didn't replace it with a stock part).
sometimes it throws a CEL, sometimes not. my 1st replacement had caused a CEL but this one did not.
overall, the procedure is pretty simple. it's 5 bolts and a single hanger. i was able to put the new cat in without taking out the rear section. you may have to take it out to expel any material that got in there though.