My brother cherokee has a high-flo cat on it, and it recently started rattling, it sounds like there are loose metal pieces inside of it rattle around. I tried putting a glove on and seeing if I could hold it still but it still rattles. Any ideas???

 

Broken

 

Broken,true.

Replace it or deal with the highly annoying noise it produces.I have the same problem.

 

^^^X3^^^
The stuff inside can come loose, the "screen" is frequently plated ceramic, which can shatter.
Sounds like he needs a new cat.

 

One of the supporting vendors sells new ones to forum members cheap.

May wanna check that section.

 

get a new cat.. the catalyst comb sometimes just breaks off, not a typical thing but possible. mostly happens when the engine starts miss firing.. the miss sends an elevated amount of unburnt fuel down the pipe which then ignites inside the cat (as designed) but the elevated amount of fuel means a bigger bang of course and can actually knock stuff loose. it will also melt off the platinum or palladium and blow it out the pipe which lessens the cats effectiveness. obdII systems should throw a code for a failing cat.