I just had my 97 4runner put through emissions and it passed but i am noticing a rattling noise as i rev the engine and it sounds like its coming from the cat converter. This happened on my 94 dodge ram so i put a new one in and the rattle was gone. Anyone else have this problem with their 4runners? I don't want to replace a working converter but the rattle is kinda trashy sounding.

 

before you say its the cat, make sure there are no hangers loose that could cause the whole exhaust to rattle

 

If your cat is rattling its done and the pieces can get in to your muffler an get stuck in there if you dont replace it soon.

 

It could also be the heatshield that is attached to the cat. Try having someone replicate the sound and just get a stick and hold onto the heatshield to see if that neutralize the rattle. If noise goes away, just unbolt it off. But if the sound is still there, it might also be an exhuast leak perhaps at weld points and or flanges.

 

heatshields and NJ dont mix...every vehicle i have ever gotten it is the first thing i tear off...and then i remember not to park on dry leaves

 

if it sounds like it is coming from your cat its the cat weather it is the heat sheild or the honey comb, most likley the later. if you have an effieciant engine the cat wont really matter. and on the flip if you have a very inefficiant engine with a brand new cat it probablly wont pass emission the cat does help but isnt the only thing involved in the process

i had this same thing you are describing happen to me on my 94 sonoma, i just ignored it for 6 months and finally all the ☺☺☺☺ broke apart and is gone now probabbly not the best aproach but i dont care it works fine now i will replace my cat when the rest of my exhaust needs it.

 

I have exactly the same ting on my 1996 4Runner.
I have been like that for at least a year and about 10K miles.
Besides trashy sound I have no other side effects.

 

I thought I had the same problem until I found a small rock in the lower heat shield of my cat. I had to cut the rock out. Don't ask me how it got in there if it wouldn't fit through the holes!

A good tactic to finding a rattle is to take a rubber mallet and lightly bang around under the vehicle until you find the culprit. Try this on your cat after the exhaust has cooled down.