'02 No Boundaries/3.0L/4X4 with 3 catalytic converters. 100K miles, occasional misfire during humid condidtions. I know about the COP issue and plan to change them. Never threw a code and only blinked the CEL a few times during the misfire until it warmed up.

Was driving home and had a sudden loss of power and a very loud squeal from under the hood. I recently replaced the alternator and I figured it was the idler pulley since the squeal changed immediately with throttle position. Only 2 miles to go, so press on. Got home and it wasn't the belt or idler. There wasn't any exhaust from the tail pipe and the Y pipe to Converter gasket had blown out. Exhaust escaping that small space made a quite nifty but expensive whistle.
I seperated the flange, and held my phone up to snap a few photos of the insides since I could not position myself to physically look into the converter.

White chunks are obviously from one of the failed front cats. but what on earth is that fibery stuff?
Photo view is through the flange looking into the front of the converter.

 

That is the catalyst wrapping. Some cats have a mesh shield on the outside. Make sure you correct the misfire or you will be doing it again. Also check the egr valve and manifold where it bolts to. I have seen more than one escape blow the egr sensor off and melt.

 

I thought of that and there aren't any signs of melting. I'm figuring the O2's and EGR will be changed with the front cats.
Wish there was a lesser expensive alternative...

 

update if anyone is following or wondering.....

I removed and dumped out the offending remnants of whichever front converter puked. Having nothing to lose (maybe?) while I save up funds to replace all 3 converters, I took a long har dlook at the front of the core in the main cat.. Most of what plugged it up seemed to be in the leading edge only of the material. I took a piece of metel and tried gently scraping off the top layer of the membrane to see if breathing could be improved to where I might be able to use the vehicle. Scrape, bang the flange end on a 2X10, scrape, bang, scrape bang... Hold it up to shine sunlight through it and it looks like it's about 70% clear and that's 70% better than when I started. Rinsed it out with a garden hose from the exit side so all material might flush out.
Held it up to sunlight, and it's somewhere around 80%.
Bolted it up to the Y pipe and started it up to properly dry out the converter. After an impressive and temporary blast of steam, It seems to run well enough to at least make short runs around town... and that's what I need to do.
Unless there is some drastic damage that can be caused by running with a hollow front catalytic converter, I think I'll be able to use it.

I'm pretty sure the computer won't like it, and it will be curious to see what codes I get. Still kind of torqued that I never got a check engine light or anything before this...

 

Did you replace the lower intake manifold gaskets. What type of spark plug you running. There was a issue with the wrong plugs burning up c.o.p 's.I used the stock Motorcraft or Autolite

 

I have yet to replace the front catalytic convertors.... ever.

I had issues previously with a misfire in humid conditions that trip the CEL, but as far as work done, I just did the COP replacements (OEM) and put in Autolite plugs. Analaysis of the failed COP's (All in the rear under the intake) revealed cracked housings like they overheated and split the plastic, but that was before.

I have yet to replace any this time. Humidity has been down and it's been running rather well as long as full throttle isn't required.

I've run almost a tank of gas through it and so far the computer hasn't complained. I guess I'll try having in inspected. Hopefully the emissions passes since there are no codes and NY doesn't do a sniff test of the exhaust.