I have the same code PO420 every 3 to 4 days and I'm running agency power catless exhaust so Its just the sensor. Just change the coils and plugs yourself (really easy) clear the codes wait till PO420 comes back on then go to the dealershit and get the new cat

 

a while ago i got engine failure warning light come on, took it to my general mechanic for service that was due and he cleared the code B2278 (unsure of what that CEL is). couple days later the engine failure warning light came back on again and took it back to mechanic again and told me "CEL P0420 : Catalytic Efficiancy Bank 1 Limit".
i've been getting back fire and high revs with small flames coming from both sides i've been told and although i can rev upto rev limiter, i feel as if i only have 95% power. on idle there is small smoke that comes out.
could my Cat. be burnt out that unburnt fuel is making it to the exhaust tips and igniting and back firing ?

 

i just pulled P0420 tonight...i have a RP SuperCat and running Cobb Stage1 Maps.

Now last week my car was really flooded by a body shop, is it possible that the flooding caused my SuperCat to start to die?

I currently don't notice any performance loss at all...but then again it just happened.

 

not really,

it caused you cat to die.. just a guess.

take it off and look at it..

beers

 

Alright, so when i take it off, what the heck am i looking for within the CAT?

 

something that looks like honeycomb.

or a melted bunch of goo. or all is gone.


beers

 

thx swoope, i'll post pics this sat when i take it off and replace it with the stock cat.

 

A bunch of Honeycomb pieces scattered about

 

I know this thread is really old but I figured I'd post here instead of starting a new one since I have a similar problem.

I'm pretty sure I have a burned out, but not clogged cat based on what I've read here. And I'm planning on going on a road trip tomorrow for a couple weeks. Should I be ok to wait to change it till I get back?

For reference I've got an 04 MT with about 135K on it, new engine about a year/15K ago. I'm feeling no performance issues, I checked the cat while warm idle last night and is not glowing red, I recently failed an emissions sniffer test, and yesterday I got the p0420 cel code, I peaked into the cat via the rear 02 sensor port with a small flexible flashlight and all I see is smooth metal walls both fwd and aft of the port.

Thanks for your help
Matt

 

yup Cat is completely burned out no sign of any honeycomb matrix.

I'm going to install the new BHR coils I got and hopefully that'll get me through my trip.

 

When you do it would be a good idea to take your exhaust off and try to shake out any possible pieces of broken cat that may be in your muffler or in the pipe.
If one is loose, it could lodge in there & block your exhaust.

 

I was just cruising down the highway when all the sudden my CEL came on. Later that night I ran the code with my cobb access port, it came up to be the P0420. There was no apparent loss in power and my cat wasn't glowing red, everything seemed to run just fine with the CEL.

car specs:
2007 AT with 67k miles on first engine
its got low compression but not so low to where it wont start at all if already warmed up although it does take quite a few cranks.
k&N drop in filter
racing beat cat back exhaust
and of course the cobb which isn't really being utilized to it's full potential

NOW for the background on what I think was the problem.

running on cobbs stock map with a few recent adjustments I made which was raising the engine load OMP to a little bit higher values for better oiling (believe me when i say it was not a ridiculous amount). Then to top it off I was premixing for a 500:1 mix which comes out to be 2oz of 2 stroke oil per 10gal of gas. Reason being is that I had read rotary gods post about the omp delete but he states if you wanted to use both stock oil system and premix he said do a very small amount like a 500:1 or 600:1 mix. I ran this combination approx 3 weeks to a month or so before the CEL came on. SO knowing that this could lead to bigger problems I went ahead a put mazdas map on and uninstalled my cobb and then went a filled up without premixing. light hasn't come back on since then which its been about 5 days now.

I know this may not have been the best of things to do, but I am just sooooooo so so paranoid about my engine getting the best amount of oil. I love the thought of adding 2 stroke oil to the mix cause its meant to be burned and adheres to metal surfaces better the 4 stroke.

I think mazda should have made a separate reservoir for only 2 stroke oil to be used in the lubricating process for the apex seals while also keeping the oil pan for the 4 stroke oil for only cooling purposes and lubrication of the bearings.


just would like the peeps who are more experienced with oiling of our rotaries share some words of wisdom. the engine is still in warranty so i'll be taking it in soon to run a compression test and hopefully get a new engine.

thanks.

 

The only useable method for checking your cat at this point is pulling it off and checking for clogs. Mine had clogged and had a massive hole blasted straight through the honeycomb and I would have never known if it wasn't for a lucky mistaken hunch and the smell (mine is one of those special 8s that doesn't show a CEL even with a gutted cat).

If your cat is gone already, switching to the stock map isn't going to help anything. You're most likely wasting your time and money running such a small amount of premix. That's next to nothing, seriously I wouldn't even bother at those levels. Most run at least 256:1 (that's what I run, and I still don't think it's enough to do much). Changing to the stock map is acctually decreasing the lubrication in your engine compared to the MM map, because IIRC he jacks up the OMP rates by a pretty good amount.

Onto other things:

The K&N drop in is probably doing more engine damage than anything else.

Nobody cares about anyone's views on what Mazda should have done, they were just trying to get a product to market.

If your engine has noticeably low compression, the little premix you're adding is going to do even less.

The Rotary Aviation OMP adapter is an option to inject 2 stroke oil through the OMP from a separate reservoir (which cannot be run dry, ever).

If anything, a failing ignition is murdering your cat and none of the mods you've done aren't hurting it all that much.

 

well that's just it, my 8 has NOT been tuned by MM, I've been running cobbs base map with increased OMP values. Like i said here recently I increased the OMP values even more which I think threw the CEL for low catalytic efficiency, I could be wrong.

I live in the deep south of louisiana which it stays quite humid so I don't think there isn't much fine dust particles to surpass the K&N filter if thats what you're implying. Really the main reason I have the K&N filter is for better gas mileage.

***I got new coils and bought new plugs for my car at 50k miles now its has 67k miles and the new plugs are already shot( probably cause i dropped them a few times while taking them out to look and clean them) and had to resort to putting my old plugs in at for the time being. I am now currently in the process of ordering some new plugs, some d585 coils (same coils that BHR uses), coil wire harness adapter for d585 coils and new ignition wires.***

when I find time to do it I will eventually drop the cat and see what it looks like, I'm just worried about stripping the 3 bolts on the flange cause I am sure they are seized in place :/.

But this is my overall plan that I am praying will work, I am pretty sure I can pass for a new engine. So I'm going to take it in to run a compression test, if they agree to getting a new engine then that's awesome, then once i get it back Ill put the upgraded ignition system in and then leave it alone and just keep mazdas tune on it forever.

 

You think a crappy air filter is going to get you better gas mileage....In an rx8....

I believe MM is the creator of the Cobb stock tune, but I could be mistaken.

You should keep reading if you want to solve your problem.

 

Also, bhr doesn't use standard d585 coils, theirs are slightly modified mechanically.

 

I appreciate the info, in my first post I said that the CEL went away when I uninstalled my cobb. The CEL hasn't come back since about 6 days now. Also I figured since I am now using my old plugs and these "OEM" coils from autozone have about 15k miles on them, that I'd just go ahead and get a better upgraded ignition system and fab up my own bracket for the d585 coils. BHR ignition system is too expensive so I figure why pay 500 when I can build it myself for 300.

 

CEL came back on unfortunately. My car now has a date with the local mazda dealership. They will be running a compression test and checking the CEL, which I know is for the cat .

 

If your cat is bad you'll ruin the engine. Check the cat.

 

I know this code is typical of cars with swapped mid pipes which i have done. But could premix attribute to it? The code only popped up after two fill ups with premix.