Glowing red O2 sensor on cat
 

So the story goes, one day my 8 wouldn't start, got it towed to Mazda for a compression test, numbers are 6.8, 6.8, 6.9 @250rpm for front and about the same values for the rear blah blah blah, engine is done for and what not. I tried doing a deflood procedure to see if that was the main starting issue besides the completely failing ignition and she starts up, but feels like she's only running one rotor :crying: . So I keep the revs at around 1k to make sure it doesn't stall out and die, and after warmed up I give her a few move higher revs, suddenly after going to a high RPM the engine runs smoothly like normal, but cuts back to the horrible powerless leaf-blower sounding mode. I shut it off and what not and decide to take a peak at the cat to see what it's looking like, and that's when I discovered that the O2 sensor on the cat is GLOWING RED. Like you just put a metal pole in the fire for 3 hours kinda red. It looked bad, I heard someone say a glowing O2 sensor means the cat is clogged, which with the ignition failure, and engine failure would't surprise me. Any input on this? Do I have to get a new cat?

Yes, your cat is bad if it's glowing from just warming up. Do not drive your car like that or you'll be replacing the engine soon.

The bad ignition dumps gas in the exhaust and the gas destroys the Cat.

Short term best solution gut your cat.

Well the actual cat itself isn't glowing red, just the O2 sensor screwed into it was. I've got BHR ignition on the way as well as new starter and new battery. I will gut the cat for the time being (thank god I passed emissions last weekend) but can you recommend any catalytic converters that won't make my car extremely loud (I already have turboxs cat back and that's plenty loud for me) and also one that doesn't burn up super fast. It needs to last.

Yes, anything glowing there at all means it is far far far too hot, the cat is clogged. Continuing to drive it will damage the engine (well, yours already is), and can eventually lead to a car fire.

The only cheap cat that appears to last at all is a metallic core magnaflow one that you have to have welded into whatever pipe you have. I'd have to dig for the part number. Everything else that people have reported slags fast under the rotary's heat and raw fuel. For example, someone tested a Davesport cat and it was blown in 2 autocross runs + the mileage to get to the event. A few thousand is the most you can expect from most aftermarket cats.

PM HiFlight999 for the part number on that magnaflow, he has had good success with it.

People never bothered to keep their maintenance up to date

I noticed a glowing O2 sensor on my car immediately after deliberately driving it hard (to see if the cat would glow or not, sort of a litmus test to motivate myself to taking it off and looking inside). But since I religiously keep an eye on the catalyst temperature, and never saw the glowing O2 sensor following normal driving, I held off, waiting to try and buy a used BHR midpipe.

Over the last week or so I've noticed that the 1,700 degrees F alarm for catalyst temperature going off far more often than normal (normally it sits around 1,500-1,600 F). Not wanting to wait and risk it any more, I finally placed my order for a new BHR midpipe. I just hope I haven't waited too long and already done engine damage. Until it arrives and is installed it's low rev's and the absolute minimum mileage possible.


I'll be forced to kill myself if I ruin the stunning compression numbers I had 10k miles ago (~9's all around).

Well the low compression on my engine and bad ignition did the damage. Or it could be the other way around, it simply doesn't matter anymore. I've ordered the BHR kit, waiting on funds for a new engine, and god help me with now this. Can't believe an oem replacement is $1200. Might have to consider a different cat. But going catless just won't fly with where I live. A rich area of town with snobby soccer moms and cops that have nothing better to do than pull over modified sports cars because they're shooting flames. The amount of tickets I'll get might just justify buying an oem replacement. Either way, I'm going to gut my cat just so I can already drive it without it exploding on me while I find a replacement. Gonna be hella loud though with my TurboXS catback lol.

the cat isn't clogged... but it probably will be if you keep trying to fracture the brick.

it's glowing because you have a bad coil(s), plug or wire... yet fuel is still going through the rotor which has the faulty ignition and burning after it exits the engine from the rotor that is actually firing.

the extremely hot exhaust is normal due to the above but not normal in that you will kill it if you keep trying.


replace your coils, plugs, wires and drive the car. just ignore the compression data and let the car tell you when the engine is done, after actually fixing the ignition issue.

Glowing O2 sensor.... strange circumstances
 

I have a 2005 RX8 with 23,000 miles on it. I recently noticed the sound was off just a bit (maybe a little lower/grumbly sounding). I got out and looked at the cat and saw the O2 sensor red hot. I setup an appointment at the dealer to have everything checked out (I just bought the car about 1000 miles ago). I bought plugs, wires and coils (not from the dealer) and had them install them while they were checking the car over. They told me they had their master mechanic working on it and he knew the cars better than anyone around the area. He noticed the sound when I brought it in, and after changing the plugs/coils/wires the sound stopped. I told them about the glowing O2 sensor and they checked the cat... said it isn't clogged... He drove the car around some also during the check up, so I assumed they would have seen it glowing again if it was going to.

All is well... or is it?

I pickup the car and drive it home (about 15 miles). The car drives totally different. Peppier acceleration, smoother idle, everything feels and sounds better. I get it home and for sanity's sake I look under the car...

I am greeted by a glowing O2 sensor...

By the way... I have never seen a check engine light yet.

I have changed the oil twice since I got the car (about 6 months ago) and I carry oil in the trunk and check after every fill up.

Any help would be great!

it could be that the middle part of the cat shattered into pieces, and you can't see it from either direction, u gotta shake it to know if it's bad.

You did right with the ignition replacement, from your description of the difference in driving it sounds like that was clearly failing. However, it also started your cat on the way to failure, so now you have to deal with that.

If they only checked the OBD2 data for a CEL to determine cat failure, then they tested wrong. A clogged cat won't throw any CEL until it throws a misfire code. Unfortunately, with a 2005, you are probably not under the 8yr 80,000 mile cat warranty any more, so I'd suggest looking for a used cat from on here, a midpipe to go catless, or hunt down one of the metallic core cats that can be welded in for you.

You can seriously damage the engine if you drive on a clogged cat.

So, this is the only thread that I could find that has a similar situation - and it looks like I do not have rights to create a new thread...

2007 RX-8 / 41,000mi

I recently noticed (~1 week ago) that there was a glowing red ring around my O2 sensor after about a 40 minute highway/city drive. I immediately checked these forums and others for a solution, and was quickly made aware that this typically indicates a clogged cat, however I'm experiencing no other associated symptoms.

-There is no power loss (compression test ~6 months ago - all good)
-There is no unusual smell, other than the typical rich exhaust the RX-8 tends to push out
-No rattle from exhaust
-My ignition system has been updated within the last 6 months (new spark plugs, wires, and BHR ignition kit)
-No check engine light
-Oil changes done every 1,500 mi (and topped off between)

I took the car into the dealer yesterday - assuming it was the catalytic converter (still within the 80k/8yr Emissions Warranty). Came back with the result that the cat is perfect, O2 sensors are reading out fine. I then thought that maybe it was the MAF sensor - also all readings good to go.

The only thing I can figure now is that it was a result of heavy driving - I'm at a complete standstill on where the issue could lie.

I feel if it was the fuel pump, I would have noticed high end drag on acceleration. If it was the ignition, it would have failed nearly instantly after installation - which doesn't make sense to me either since it's been fine up to this point. All the emissions equipment seems alright as well.

Is there anything that I'm missing?

Yes, the part you are missing is that the dealer tests will NOT detect a clogged cat, which is what will cause the glowing.

The dealer's sensor tests will always read fine because the exhaust that IS getting through is still getting filtered by the part that isn't clogged.

Imagine a garden hose with the water on and a nozzle. Open the nozzle a bit. The dealer test is equivalent to checking: "Is water coming out?" It does not measure pressure buildup or flow restriction. It's one of the key failing points dealers have.

Usually, it requires dropping the front of the cat and looking inside to see if it's clogged, and dealers don't do that unless pressured to do so.

That what I had suspected, and am about to call the dealership today to request how exactly they did test the cat. I just hope the condition of the cat is severe enough to be covered by a warranty.

I have checked under my car on every drive for the last week and I have only seen the glowing ring twice (the second less severe than the first due to low-rev driving).

Is this severe enough to merit replacing the spark plugs yet again? And should I follow up with a second compression test?

I can't do any work myself since the car is still completely under warranty and I'm trying to maintain flawless service records, so the options for DIY are highly limited (I also have very limited tools).

Hello rotary brothers. RX8 - 2005 - 80k. Would love to get someones opinion on this. Got a cel P0420. Recently change ignition system so thats fine. Notice after a hard drive I see a red ring around the o2 sensor(not anywhere else). No bad smells or (powerloss)<- I think. Warranty is gone. I research and found out that cel could be a number of things. For ex. both sensor are not working right, exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter. Is is possible to run testes before assuming my Cat is gone? Thx in advance.

Your cat is damaged. P0420 is virtually always cat damage. The glowing ring around the O2 sensor confirms it. Verify with a visual inspection. Scroll down on this page (RX8Help.com: Solving Misfires) to where it references Bad/Clogged cat, and I've got some pic links there for what it should look like and what some failure methods look like.