Red Hot Cat

[paulo57509]

On my way home to the central valley from the bay area last night, my car lost a plug or wire or a coil (haven't diagnosed the problem yet) just outside Milpitas. I drove the car back to Mountain View (about 15-20 miles) to pick up another vehicle. When I parked the car, the cat was glowing red hot; just a little...not the entire unit.

How much heat can converters tolerate before they're really fried?

 

[BuickGN]

They can tolerate a lot but when the entire shell glows that's pushing it. It's from the raw fuel reacting inside the cat so who knows how high the internal temps were. I want to venture a guess that if the catalyst didn't melt and plug up the exhaust you're probably ok but there's a smog guy on here that will probably prove me wrong.

 

[Colt45ws]

Next time you have to drive on a car with a bad misfire, unplug the injector for that cylinder. This will prevent fuel wash down of the cylinder and possible cat damage.

 

[JTK]

Originally Posted By: paulo57509
..How much heat can converters tolerate before they're really fried?


Not much if it's a late model vehicle. There's little 'extra' capacity built into them. Omno's got a great idea though. No fire is better than a misfire! Excess fuel loading is BAD for modern day cats.

Joel

 

[Familyguy]

Originally Posted By: JTK
Originally Posted By: paulo57509
..How much heat can converters tolerate before they're really fried?


Not much if it's a late model vehicle. There's little 'extra' capacity built into them. Omno's got a great idea though. No fire is better than a misfire! Excess fuel loading is BAD for modern day cats.

Joel


Agreed. The older cats were a bit more "hardy" in this regard. A few minutes of cherry red is probably OK, but driving it like that for 15-20 miles is really pushing it. I guess he'll find out for sure when he has his next state emissions inspection.

 

[JHZR2]

THe washcoat in the converter may have become mobile, melted, agglomerated, or lost its reactive characteristics due to some other mode of degradation.

That said, if it is an OBD car, youll quickly get a CEL telling you that the cat performance is unacceptable. However, you may have fried the downstream (and also upstream) sensor.

Youll have to see how the car drives and operates. I'd definitely change the oil too.

 

[mechtech2]

Keep an eye on it.
Modern cars have 2 or more O2 sensors to tell if the cat is puked.
Poor performance is another indicator - it could be melted or broken internally and plugged.

 

[Benzadmiral]

Gee, I thought this had something to do with overheated felines. . . .

 

[paulo57509]

The car is a '92 Lumina 3.1L V6. OBDI with no secondary O2 sensors, etc. I just need to run it for a few minutes to determine which cylinder(s) are electrically dead. With DIS ignition, I figure a few seconds with a timing light on each plug wire should tell me which one is dead.

 

[paulo57509]

Just to close the loop on this one....

Timing light as a diag tool worked great. Coil for cylinders 3 and 6 had died.

Working on this car isn't too difficult; you just have to remove a bunch of stuff to get to even the most mundane fasteners. Removing a fender brace and the air box just to be able to disconnect the battery is ridiculous.

With regards to the cat, we will have to wait until the next scheduled emissions test.

 

[mechtech2]

You are lucky that the ignition problem was one that a timing light check could determine.
It could be many other things that it would not detect.

 

[artificialist]

Originally Posted By: Familyguy
Originally Posted By: JTK
Originally Posted By: paulo57509
..How much heat can converters tolerate before they're really fried?


Not much if it's a late model vehicle. There's little 'extra' capacity built into them. Omno's got a great idea though. No fire is better than a misfire! Excess fuel loading is BAD for modern day cats.

Joel


Agreed. The older cats were a bit more "hardy" in this regard. A few minutes of cherry red is probably OK, but driving it like that for 15-20 miles is really pushing it. I guess he'll find out for sure when he has his next state emissions inspection.

Nonsense!

My dad had a 1979 Toyota Corolla and a failure in the AIR pump cause the car to quickly glow red and then melt!