[jjxusaf]

As many of you probably know do to my numerous recent posts, my stang is running like crap. I've been systematically checking parts to no avail. At idle she sounds like what you'd expect a 68 stang with a 4 barrel and glasspacks to sound like, bouncing between really alive and almost dead.

Anyway...tonight I re-located the battery from the trunk back to the engine compartment just in case that was the problem. After I finished I started the car up and did the usual walk around check. Well, I noticed that there was an audible rattle / ticking sound coming from underneath the car around where my catalytic converters sit. Is there anything about cats that could cause a rattle, almost like a valve tap sort of sound? Or are the sounds of my heads just being echoed in the exhaust? Because when I'm driving my car sounds like a diesel and this H-pipe is used from a guy who rolled his stang. On the other hand I just passed smog with flying colors. Any advice is much appreciated. Thanks.

[Vortex]

could be something broken inside the cats but still filters... the only thing to worry about there would be sound..

[Duke of Earl]

Maybe an exhaust leak...? Probably a dumb answer... but the idle on my IR*C was pretty bad, and part of the problem was an exhaust leak... the other was a bad O2 sensor...? Something like that... I will check my records to make sure...

[jjxusaf]

not an exhaust leak....checked that out thoroughly...thanks anyway

[unknown]

possibly a loose heat shield or the air tube that goes into the h-pipe

[90LX50T5]

It's the cat convertor. The substrate that holds the catalyst chemicals has broken apart and rattling. Dodge trucks are bad for that, I know the sounds. If it gets bad enough it will start to plug itself up. If the car was rolled, it probably jarred it loose.

[Lone_Star]

i had the same problem with my stock h pipe, and was told that the inside of the cats was plugged.