epj993

When I rev my 993, it makes a hollow vibration noise when the RPMs come down to idle. It sounds like something rattling inside something. I can't hear this while driving - even with the window down - but if I rev at a standstill or in the garage it's audible.

Since I just did a SAI flush within the last month, I checked the bolts on the HEs and exhaust and they appear secure. If this were any other car, I'd say it sounds like a loose exhaust bracket. But, being a 993 I'm not sure.

Thoughts anyone?

Bull

Loose exhaust baffle in one of the mufflers?

epj993

I guess that's possible. The car came with the Motorsound option, but the PO apparently sent the mufflers out for a RSR-waanabe mod - nice throatly growl though (the mufflers have the original part number).

If that's true, sounds like no real problem but just an annoyance.

Anything else possible?

the_buch

I have a rattle in the exhaust system when cold, and when warm a weak hollow sound on return to idle ... I have been thinking these are unrelated ... am considering the RSRs which will allow me to solve both problems even if independent ... good luck and keep us posted ...

Traffic53

yep. i have that too (also have unmodified motorsound pkg).

BobbyT

I had the same sound, and checked the exhaust system, heat shields, even tried putting a piece of carpet between the fender and liner, but nothing helped. It went away (or my hearing has gotten even worse).

Caveman

Sounds like a loose heat shield?

96C4S

mine was just an ajustment of the exhaust clamp that joins the muffler to the coverter tiny air leak causing this sound on the drop off of revs. Get someone to start the car will you lay behind and feel around the clamp areas while exhaust is still cool thats how i found mine.

Alon

I find that sometimes, small rocks (gravel, etc.) get lodged between the rear bumper cover and its heat shield (just behind the rear wheels). When they get stuck in there, they just rattle around at lower revs and eventually bounce out. I've had to go in and loosen the front heat shield bolt, seperated the shield from the bumper skin and then pulled out the little bastards - noise gone. Aside from that, check all clamps, mounts, etc.

amfp

I have apparently the "same" sound. If rev in neutral to about 4K RPM and quickly back off, I hear a very brief rattling sound. Nothing is loose. My thought it is Varioram - and is nothing to get concerned about unless got worse.

Marv

What you describe may be normal. The stock 993 has a sort of hollow muted gurgle when RPMs drop after blipping the throttle.

This noise is pretty muted and does not have a sharp rattle like loose metal. There is a distinct difference between this sound and vibrating metal.

Does that describe what you hear?

epj993

No, it's not a muted gurgle - it is more of a hollow metallic sound. This weekend I'm going to try and locate this per the suggestions here. I'll post my findings.

tam993

funny, I have a motorsound pkg on a 96 993 and it rattles sometimes when you rev it and let the throttle back off slowly. It rattles around the 1-2k rpm spot.
I can't figure out what it is, it comes and goes.
Sounds like it's some kind of metal to metal sound (vibrating) like a heat shield.
I guess hitting things with a rubber mallet might help me find it.