Disintegrating catalytic converter

[David_073v]

Hey yall, I got lth 5 months ago with hi flow cats but didn’t get a tune. I notice this rattling sound from the drivers side. I tapped my driver side cat and it sounded hollow but my passenger side sounds normal.

Does this usually happen when you don’t get a tune?

 

[Jonas1ne]

Not usually. No tune by itself generally wouldn't make a hi-flow cat start rattling. If one side sounds hollow and you're hearing rattling from the driver side, I'd be more suspicious of the cat substrate breaking up internally, a loose heat shield, or something in the exhaust connection vibrating.

I'd check

• Heat shields and clamps first
• Whether the rattle changes with RPM
• Any CEL / catalyst efficiency codes
• Exhaust leaks around the header/cat connection

If the cat itself sounds loose inside when tapped compared to the other side, I'd get it looked at sooner rather than later before debris moves downstream.

 

[David_073v]

Not usually. No tune by itself generally wouldn't make a hi-flow cat start rattling. If one side sounds hollow and you're hearing rattling from the driver side, I'd be more suspicious of the cat substrate breaking up internally, a loose heat shield, or something in the exhaust connection vibrating.

I'd check

• Heat shields and clamps first
• Whether the rattle changes with RPM
• Any CEL / catalyst efficiency codes
• Exhaust leaks around the header/cat connection

If the cat itself sounds loose inside when tapped compared to the other side, I'd get it looked at sooner rather than later before debris moves downstream.

Thanks. I heard if you don’t have a tune you run a little rich so I didn’t know if it was a case where unburnt fuel was igniting in the cat causing it to overheat and break up internally. I hope this isn’t it and something else is loose.

 

[StockishS197]

Thanks. I heard if you don’t have a tune you run a little rich so I didn’t know if it was a case where unburnt fuel was igniting in the cat causing it to overheat and break up internally. I hope this isn’t it and something else is loose.

Rich won’t kill cats, usually the opposite. Lean makes the substrate heat up and melt.

the factory strategy uses fuel to cool the cats via increased fueling during cat over temp.

Cats usually break down when it gets too hot and/or it hits something. Ceramic substrate does this more commonly than metallic.