SOLVED: Cat Red Hot - Carpet Melted/Charred

[gnarlybus]

My buddy is giving me his 89 Bronco II XLT 2.9L 2WD. He has an issue with the catalytic converter getting really hot and melting the carpet (then charring it) inside.

At first I thought, ok no problem, I'll replace the cat and be good to go. But now I'm concerned that after replacing it nothing will change.

There is no lack of power or audible miss in the engine. He drove it 65 on the freeway and had to keep pulling over every 20 mins because it would get so hot, but it had power.

I have to drive 5 hours to go get it and bring it home so I'm trying to be prepared. I figure I'll warm it up and check each cylinder for spark and make sure they're firing. Then I'll get underneath with a laser thermometer and check the temps before and after the cats. Anything else I could do to be prepared?

I don't want to spend the cash just to have the cat get toasty again.

 

[Uncle Gump]

If the converter is getting that hot... it is a fuel issue. The thing is running to rich.

 

[alwaysFlOoReD]

^^^Agreed. Check fuel pressure regulator for gas smell in the vacuum line. Should change o2 sensor too.

 

[gnarlybus]

Is there only the upstream o2 sensor or are there 2 on the 89?

Are the Haynes or Chilton's manual worth getting or should I pay extra for the official one?

 

[alwaysFlOoReD]

1 upstream. Make sure there are no holes or leaks ahead of the cat.

 

[Snoranger]

While you're checking pre and post cat temps, check the manifold temp at each cylinder. That can lead you to a misfiring cylinder.

 

[gnarlybus]

Will do. I'm thinking that if I can't figure it out, I'll disconnect the cat and drive it home loud.

Sent from my LG-US996 using Tapatalk

 

[adsm08]

Will do. I'm thinking that if I can't figure it out, I'll disconnect the cat and drive it home loud.

Sent from my LG-US996 using Tapatalk

That cat is probably damaged. It may be better to punch it out and drive it home quiet. That should be left up to how it looks when you pull it off.

 

[gnarlybus]

I'm picking it up from a storage lot where I can do tests and stuff but I don't know how much work I can really do to it there. There is a muffler shop up the road that said $100 to swap out the cat with a new on I provide, but I don't want to ruin the new one before I figure out what's wrong.

How easy are to access are the flange bolts to get the cat off? I'm thinking I could breaker bar it maybe. Otherwise I could have the shop take it off and then go home. I'm not sure if they'd put a gutted one back on in CA even though its registered in OR.

Sent from my LG-US996 using Tapatalk

 

[gnarlybus]

Does anyone know what size wrench the nuts holding the cat to the Y pipe and the bolts holding the cat to the muffler are? It would help me out. Thanks!

Any tricks to getting at that hard to reach nut on the cat to Y pipe junction?

 

[bobbywalter]

its this size....

 

[gnarlybus]

14mm

 

[JerryC]

See if the shop will put a cheap aftermarket cat on it. I had one put on mine, it works fine but may not last as long as the factory one. But it will get you home.
Just a thought, maybe the heatshield fell off. If so maybe the shop could fab one up for you.

 

[gnarlybus]

Thanks. I'll look for the heat shield when I get under there. They quoted me $450 to replace the cat!

Sent from my LG-US996 using Tapatalk

 

[scotts90ranger]

Cats getting hot need a burnable air fuel mixture, usually a lack of spark to a cylinder from my experience from tech calls at work. Just extra fuel will NOT cause an exothermic reaction in a cat, you need oxygen as well, gasoline doesn't burn as well past the stoicheometric ratio so add more fuel and you get less fire, that's why you add more fuel when running hard to cool the exhaust valves...

Anyway, that said I'd look at the plugs and wires, from what I have hard I wouldn't think a TFI module would do that since they're usually all or nothing, same with the pickup in the distributor, could be a bad cap though...