Misfire and cat damage

[GreigM]

I see on the OBD codes that a misfire can cause CAT damage - does anyone have an idea how quickly this will happen, or is there any way to test for cat damage (CEL light for example)?

The reason I ask is that I changed plugs myself a while ago and because of poor connections had a misfire, which for reasons of stupidity took a little while to diagnose - I didn't drive more than 1/2 mile with the misfire, but started the car for a few seconds on about 15 occassions until I found and corrected the problem - will the cat on the misfiring side be damaged?

[Loren]

If you have a cat damaging misfire the CEL would be flashing (instead of being on steady). A flashing CEL always means "potential damage to the cats".

[GreigM]

On this occasion the CEL did come on (steady), telling me of the misfire, but once I corrected it I had a friend reset the CEL - so can I assume no damage was done?

[0586slb]

Don't worry about it. Cat damage occurs when unburned fuel (from a missfire) enters a fully warmed Cat. Burning the fuel in the Cat can result in a core meltdown or cell failure, due to overheating.

However, I doubt the Cats were anywhere near lightoff temperature. In fact, every time you start the engine, unburned fuel is entering the Cats, but when the engine is cool and fuel enriched, the Cats are cool too and the Catalytic Conversion process is not taking place. (I could waffle here about open loop lambda control during warm-up etc)

We have pre and post Cat lambda probes too, the post probes do very little to correct the fuel mxture, rather they verify the performance of the Cats. So if your light stays off, everything looks OK.