is it possible for something to be stuck in the cat? theres something rattling down there and it sounds like its in the cat. its not a new cat either so its not like somethnig was in there during instalation

 

its probably your heat shield...thats what it was on my truck when it soudned like the cat was rattling.

 

lol dont you find it funny when you think your on to something complicated but yet it turns out to be the most simple thing ever?

thanks ill look at that

 

Agreed...

 

might be the internals though to...


Lamm

 

My buddy had an extremely clogged cat on his truck and he heard a rattling, he removed the heat shield and the sound was still there, so he replaced the cat and asked the exhaust shop to let him have his old one. He took it home and cut it open...turns out the buildup on the sides of the cat had come loose and were rattling around in there...odd, but I guess it can happen.

Fink

 

hm, how can i tell if its clogged?

 

You would probably notice a loss in mileage, nothing huge but a difference nonetheless. The way I could tell on my old rig was driving around at night and then stopping with the rig running, the cat was glowing red it was so hot...usually a good sign something isn't right. lol.

Either that or on my 3rd gen it triggered the CEL.

Fink

 

Using vacuum gauge is the easiest method.

Starting with the engine at idle, slowly increase engine speed to 3,000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3,000 RPM. If vacuum decreases at higher engine RPM's, an excessive exhaust back pressure is probably present.

 

This is what i've been told by a few guys at muff shops and others: Knock on it with your fist. If it makes an obvious but unusual internal rattle, it needs to be replaced.