P0430 and hollow knock

[tampa996]

I have an 02C4s. A few weeks ago I started hearing a hollow infrequent knock at idle that has become more regular and noticeable over time. At first it sounded like something was loose and was just intermittently rattling as the engine was at idle (exhaust or something in that general area).

2 weeks ago the car threw a CEL for a misfire on cylinder 1, which was attributed to a cracked ignition coil that got wet during a Florida monsoon. I replaced all of the plugs and coils (as I just crossed 60k miles) and the car has run great for 2 weeks.

Today on the ride home I threw another CEL with code P0430. The most likely suspects are a bad Cat or O2 sensor, but I am unclear if either of these would produce the knock I am hearing underneath the car. Would the Cat or O2 sensor contribute to a hollow knocking sound at idle? Is the P0430 typically attributed to a bad Catalytic Converter/O2 sensor or is there anything else I can take a look at given the tapping sound I am hearing from the engine?

Edited February 15, 2014 by tampa996

[Ahsai]

Most likely your bank 2 cat (passenger side) is physically broken inside hence the knocking. You can put a screwdriver between it and your ear to check for the knocking noise. P0430 alone is likely the bank 2 cat since bad o2 sensors have their own codes.

If you have a scanner that can read O2 sensor values in real time, check out post #22 here

http://www.renntech.org/forums/topic/43522-p2096-porsche-fault-code-16-oxygen-sensor-ageing-delay-bank-1/page-2

Edited February 15, 2014 by Ahsai

[Silver_TT]

As Ahsai said, you will want to do the due diligence and read the O2 sensor values (very easy to do with a Durametric, especially if you read that post) but I also think your cat is bad given the code and what you have said. I went though the same thing on the exact same car.

Also, this isn't a fact but it's my strong opinion after doing a lot of reading back when that post was made: The 2002-2004 C4S have cats that seem to go more often after 60-80K miles (the C4S in fact has cats with a different part # than its brother and cousin, the C2 and Turbo). This is disproportionately more common on the C4S cats for some reason. I don't really have the exact answer to why that is but one thing I noticed after switching from the C4S to a Turbo was the Mezger seems to run with a lot less vibration in the exhaust (making them last longer). Just my personal opinion as the result of my own experience with the same issue.

Edited February 16, 2014 by Silver_TT

[tampa996]

Digging up an old thread, but I finally got around to ordering new headers and cats from fabspeed. Will be bolting them on this weekend, hopefully it will be a painless endeavor!

I have read 19 ft. lb. torque on the header and 22 ft lb. on the cat., can anyone confirm this?

How about a torque measurement for the O2 sensors?

Edited May 2, 2014 by tampa996

[Loren]

Digging up an old thread, but I finally got around to ordering new headers and cats from fabspeed. Will be bolting them on this weekend, hopefully it will be a painless endeavor!

I have read 19 ft. lb. torque on the header and 22 ft lb. on the cat., can anyone confirm this?

How about a torque measurement for the O2 sensors?

Header 19 flb.is correct.

Cats and O2 sensors (using the proper tool) are 34 ftlb.