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I installed a supposedly new OEM cat from Mazda. It arrived a little banged up. I drove for an hour one day and 30 mins another to clear codes for emissions. Both times after pulling into the garage at night I can see a very faint ring around the o2 sensor. I tried to take pictures with two different phones, but it doesn't catch well on camera, nevertheless I can see a faint glow. Is any amount of glowing bad? It's coming from the unshielded exposed area around the o2 bung, which I think may be thinner.
Car is running great, LTFT stays very close to 0. No hesitation or starting issues. Was previously running rich from a slightly loose sparkplug I think, or seafoam cleaning fixed it, but it's been good, hence I thought it was safe to install.
Maybe in compelete darkness you may notice a glow, but really it shouldn't be apparent.
Is your ignition healthy? Why was the old cat replaced and what condition was it in?
Steel starts to glow faintly around 900°F. Cats typically work at around 500°F, but can get much hotter. Internet says 1200°F under load. Rotaries notoriously run hot, so 900°F doesn't seem out of the question. I can't check mine for your because its put away for winter, and the roads are nasty right now, but maybe someone in a less snowy location could check for you. If everything else feels and instruments out well, I'd keep an eye on it, but otherwise assume all is well.
Maybe in compelete darkness you may notice a glow, but really it shouldn't be apparent.
Is your ignition healthy? Why was the old cat replaced and what condition was it in?
I was having an extremely intermittent issue where sometimes the STFT would go to -25 and stay there and then the LTFT would start to trend towards -25 too. It was accompanied by occasion misfires at higher rpms and shuddering when pushed harder. Sometimes the brake stomp reset would work for a while. Eventually, while gathering more data one day it started running rough and would turn off unless I gassed it to keep it on. Finally got the p0420 code that day. Removed the cat and the front honeycomb was cracked/exploded. Gutted it and put it back on. It's been like that for a year. Finally, had to get a new cat to take emissions test. As far as I know that was the original cat and I got the car with 105,500 miles. I am currently at 109,967.
I have BHR ignition coils with wires and plugs provided by him with about 2,000 miles on them. I checked them with an HEI spark tester several times and then eventually a timing light. So, then I suspected a bad pump resistor and then front o2 sensor. Before I was about to install the new o2 sensor I ran aerosol seafoam through the intake, then I saw a leak from the rear leading spark plug when I hot soaked the car. The spark plug was loose even though I had used a torque wrench when installing. Way back when, the misfire led to pending P0302 in torque app, so maybe that makes sense if the plug was loose leading to a rich condition. I am not sure in the huge temp differences in AZ and driving hard vibrated loose that one plug as I started to use the vehicle less, like once a month. After seafoam plus tightening that spark plug it runs great and I never installed the new o2 sensor. The fuel trims are now close to when I first installed the BHR ignition. I had been driving it and haven't had any issues aside from the code for the gutted cat. I installed the new one and reset codes and it has still been good.
Please tell me I just have good eyesight at night, and that I am being paranoid because that faint glow is normal lol.
I had that faint glow without ANY other symptoms and after my car had been checked out and given the OK from a mazda dealer. I bought it on bring a trailer....the faint glow spooked me and i replaced the ignition components and hoped it would go away. it did not. I had a local muffler shop install a magnaflow. (welded in). my old cat looked perfectly fine on the inside. I wonder if it was bad now that i find people saying a slight glow is normal. I couldnt bring myself to keep driving it after finding photos of cars on fire etc etc.
Steel starts to glow faintly around 900°F. Cats typically work at around 500°F, but can get much hotter. Internet says 1200°F under load. Rotaries notoriously run hot, so 900°F doesn't seem out of the question. I can't check mine for your because its put away for winter, and the roads are nasty right now, but maybe someone in a less snowy location could check for you. If everything else feels and instruments out well, I'd keep an eye on it, but otherwise assume all is well.
I will see if I can check the cat temp again with torque but I don't how accurate the number would be as I am not familiar with where that number comes from. After emissions that new cat is coming off. I just want to know if any glow is okay. The one Mazda sent is a bit banged up, but I didn't hear anything when I shook it. So, I will ask for an exchange, if necessary, but the car has been running well and the monitors on torque look good. I will use a better camera to see if it picks up what I see, and my two phones could not capture.
Praying that it is normal, and Mazda didn't screw me.
I'd be less worried about the cat itself being a problem, than the root cause of the original issue still being on the car. But like spectre said, it's a matter of the *outside* of the cat reaching glowing temp. It's absolutely glowing inside at all times, the cat rarely goes below 900F, and from watching the data it seems to get hottest with slow driving/traffic. Under medium load it seems to cool down. Given that everything is new, I'd keep an eye on it but not intervene if it doesn't get worse/no other symptoms appear.
If you're in pitch darkness and your eyes have had time to adjust to night, you might be picking up faint light that wouldn't be visible under normal conditions. It doesn't sound like the surface of the sun glow associated with actual cat failure.
AFAIK the cat temp signal is inferred from rear O2 sensor impedance, but it's not a dedicated thermometer... more like an informative side effect.
I got the temps from torque. On a cold startup it was around 1300F. Fully warmed up on freeway at 65mph it was just under 1600F. Temps dropped like 1-2 hundred degrees on local. After driving, idling in my garage, the temp went back to 1300F in under a min. It might have continued to drop but I turned the car off. I live about a mile from the freeway.
I am assuming my previous issues are fixed since the car is running smooth and torque is showing that my LTFT is close to 0 with a small fluctuation of + or - 2-3ish. No CEL and nothing pending for a few drive cycles now. It's got enough power to break traction and freely pulls through 9k rpms.
Do you think that I missed something, and the problem that murdered the cat still exist? I don't know what else to check. I also wasn't able to see any glow during the day while inside the same garage during a similar drive length.
For reference, I used to see a faint glow ring around the O2 sensor of my RX-8 when I drove it hard at night and I took a look a couple of times. The cat looked fine inside when I took it off to inspect it.
And well, if you have already fixed the other issues then there isn't too much to worry about here. Rotary does have pretty hot exhaust gas. If you drive it hard, then the car will also run a little richer, so that's also more fuel in the exhaust = hotter cat.
Steel starts to glow faintly around 900°F. Cats typically work at around 500°F, but can get much hotter. Internet says 1200°F under load. Rotaries notoriously run hot, so 900°F doesn't seem out of the question. I can't check mine for your because its put away for winter, and the roads are nasty right now, but maybe someone in a less snowy location could check for you. If everything else feels and instruments out well, I'd keep an eye on it, but otherwise assume all is well.
12-14-2023, 05:41 AM
