Quick Question: How do you differentiate between a pre-cat's rattle and a heat-shield
 

Have a heat-shield rattle at something like 2200 RPM. Rattles on the way up in any gear or neutral. Does the cat rattle happen any time under acceleration, or only at certain speeds?


Also have a P0420 for a naughty cat, so I wondered if maybe it was the guts of the pre-cat rattling instead. I heard someone on here, Rochester?, describe it as "shaking bees in a tin can," but that's a lot like a heat shield rattling, right?

No, I haven't started troubleshooting the P0420 yet, but it just crossed my mind the other day so I figured I'd fire a shot across the bow and see what's what.

Best way to diagnose between the two is remove your heat shield(s) and see if the rattle is still present.

(Damn you, foodmanry. You beat me by 2 minutes. Meh, I'm leaving this post anyway.)

Eirik, your front pre-cat heat shield is original equipment, right? As such, it's probably pretty trashed and corroded by now. So rip it out, and if the noise is gone, you have your answer.

That's what my mechanic did last month. The noise did not go away, and so I have no answer. I suspect one or both pre-cats, but the noise isn't actually localized anywhere, so now I suspect Nargles.

But it reads like your problem is entirely different than mine.

Maybe we could make videos of our noises and compare? I have a nasty rattle while the RPMs come back down, and whether it's pre-cats or shields, headers are going in soon.

If you don't want to remove the heat shield for whatever reason, you could get a bolt and hammer it between the heatshield and the cat. This way, the bolt is held on there by the heatshield and cat and the heatshield wont rattle.

This way is pretty easy and you don't gotta remove the heat shield.

When my rear pre-cat started rattling it did it more on a decel at lower rpms and the rear bank pre-cat is mesh inside and the front bank is ceramic inside so the front wont rattle i don't think.I diag'd mine buy putting the car on a lift and holding the rpms where it made the most rattle and had a tech underneath with a pry bar putting pressure on all the heat sheilds and they were fine so he chased the noise above the tranny to the pre-cat,dropped it,gutted it,no more noise,more power and better sound.I left all the heat shields off after we gutted them just cause.I got a ses for bank 1 and 2 catalyst efficiency codes..need sims but don't need a sticker till march so im ok for now

Header time nao.
:p