Cat rattle ?????

[Brickermaxwell]

My 2004 GT has this rattle at about 1500-2000 RPM with medium load. It sounds almost like a loose heat shield but I feel like that would be much more noticeable. I already had the driver side rear cat go bad and throw code, but I used O2 sensor spacer to get the code out. Could it be the inside of the cat making this noise? It's hard to tell.

 

[Terrorist 5.0]

My 2004 GT has this rattle at about 1500-2000 RPM with medium load. It sounds almost like a loose heat shield but I feel like that would be much more noticeable. I already had the driver side rear cat go bad and throw code, but I used O2 sensor spacer to get the code out. Could it be the inside of the cat making this noise? It's hard to tell.

Hard to tell without a video so we could hear the sound.

A rattle under load is typically a good indicator for detonation.

 

[ttocs]

that is what mine sounded like when it went bad, there was also small solid pieces come out of the exhaust after a while.

 

[Terrorist 5.0]

A failing/plugged cat sometimes gives off a rotten egg smell when accelerating hard. Happened to me in my old LS400 I had a couple years back. If you are hearing this rattle along with the egg smell, then a new cat/cats are probably your best bet.

 

[cobrajeff96]

Rattled your mom's cat.
(Sorry, I couldn't resist)

 

[Miltoid]

Get under there and tap it with a rubber mallet to try and duplicate the rattle.