I have a 2008 231 rx8 which passed its inspection two weeks ago.
The code for cat efficiency has come on a couple of times within the last few months.


I have noted a an airy rasping from the car on acceleration and deceleration (sounds like an exhaust leak but no leak is present.


Now the cel with P0420 code come on after two drives each time I reset it.


The cat temperature was recorded by the ECU as 867 degrees centigrade at 3500rpm while cruising.


The honey comb of the cat looks intact but could they be blocked?
The car runs fine and drives well except for the noise.


Thanks


Antony

 

I'd guess it's plugged up somewhere. Same thing going on with my car recently and I've also experienced some hesitation when accelerating hard. I'll pull it off and look at it when I get a chance but I don't plan on keeping my 8 much longer so if the CAT needs replacement I won't go the expensive route. A cheap one with some kind of warranty is all I need at this point.

 

Sometimes it can be hard to really get a good view of a clogged cat. Just because the honeycomb in the front view seems good doesnt mean its not backed up somehwere else. I also had a clogged cat a few months back. Because I had recently had a compression test I knew that my engine was healthy, so I went the route of a BHR midpipe. I paid $350 for a used one on the forum with low miles. I then mated that with a Cobb Accessport which cost another $350 to mask the CEL and pass inspection. This route made much more sense for me since it freed up some horsepower and I will never have to replace it again since there is nothing to clog up or burn out. The fact that it cost me $700 instead of $1500 for a new factory cat helped make the decision an easy one.