Yes, a plugged cat can cause overheating. Time to pull the oxygen sensors and take her for a drive.

 

You fixed the misfire but the damage has been done to the CAT or CAT's from the misfire and Tom is likely correct on his diagnosis.
Unburnt fuel hitting the CAT's from a misfire will very quickly destroy the front of the converter with the exploding unburned fuel.... Been there done that in literally 20 miles.

 

check and or replace the coil , also the TFI ignition module can be a issue with age and heat ,
could also be a bum injector. good luck

 

No, The upstream cat collapses and plugs up the downstream cat. You can pull the upstream sensor to breath but you loose the ability to set mixture properly when you pull the upstream sensor. Pulling the downstream sensor will bypass the blockage at the downstream cat and still allow proper mixture setting since the downstream sensor is just there for fun.

It's possible that the upstream cat plugs without collapsing into the downstream cat, but I've never seen it.

 

I could be barking up a wrong tree but I've seen it time and time again on our vehicles. Steady misfire on bank 2 cylinders. Reduced power, problems at full throttle, sometimes even a clanging sound in time with RPM that makes you think you've got serious engine issues. It might start gradually with just a couple misfires now and then and grow.

 

Interesting, I've never worked on a vehicle with an exhaust setup like that. Everything I've seen has both converters before the downstream sensor.

 

x 2, i was another with a clogged or excessively restricted secondary catalytic converter, it was so restrictive i couldn't even hear the engine run, just a whoosh of air exiting the pipe, mileage was horrible and it struggled to climb a hill, confirmed the restriction with a no-touch thermometer then removed secondary converter and replaced muffler with low restriction unit and the difference was night and day, totally different animal now and runs better than i could have hoped for..
Still has a misfire but that has been positively linked to a clogged injector, there is also an intermittent stumble but that is the result of the ECU having an intermittent 'brain fart' and is what i consider as normal for these vehicles because of the limited processing power that was available when these ECU's were designed and built..
When diagnosing a misfire or stumble you need to take all these factors into account and rarely is it ever as simple as replacing plugs or wires, ..

 

That's the setup in the van 4.6 and 5.4 V8s and I think the 6.8 V10 also.

 

my van had a cat so clogged, the backpressure broke the pass side exhaust manifold (single exhaust van), literally busted the manifold. Covered engine bay with black greasy exhaust fumes all over everything, this is from the prior owner, I have about everything sorted now. When the cat came off, it was like lava rocks coming out of it by the handfuls.