[V6-12v] Dead cat?

[James Whitehouse]

Having had two original cats die on me shortly after buying my V6, I'd say
the rattle sounds like it's possibly a cat. As for the sudden power loss, it
could be a number of things. Personally I didn't have any power loss when
either cat failed, but they were more likely fractured due to thermal shock
and impact damage over the years on country roads than burned out due to
dodgy O2 sensors.

Since your O2 sensors are new, I'd personally be a little surprised if the
cats had suddenly burned out. Other causes for this apart from the O2
sensors can be the engine burning too much oil (the oil goes back into the
cats and burns there) or something like a dodgy spark plug (unburned fuel
goes back into the cat and burns there.

Non-cat related reasons for a sudden power dropoff are too numerous to
mention in full, but could be anything from coils, to speed/ingnition
timing/hall sensors, etc, to MAF sensor... go through the usual list, I'd
say.

I don't know, but I'd definitely investigate other possibilities before
shelling out good $$ for a new cat...

James


> -----Original Message-----
> From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com] On
> Behalf Of Joe - Audi
> Sent: 10 December 2006 22:40
> To: Kent McLean
> Cc: Audi list
> Subject: Re: [V6-12v] Dead cat?
> 
> 
> On Dec 10, 2006, at 8:49 AM, Kent McLean wrote:
> 
> > Tom Christiansen wrote:
> >> Marc,
> >>
> >> I changed the O2 sensors last year some time. I haven't had any
> >> trouble codes thrown.
> > ...
> >> On 12/9/06, The CyberPoet <thecyberpoet at cyberpoet.net> wrote:
> >>> When they melt, they can block up the passage, causing significant
> >>> back-pressure which can cap the power availability (esp. RPM's)
> >>> coming out of the engine.
> >
> > You might want to unbolt the cat and shake it around to see
> > what falls out. If that clears it, you could bolt it back on,
> > ah, just for testing purposes (yeah, that's it), to see if power
> > comes back.  Of course, to pass emissions testing, you'd need a
> > new cat. Maybe. ;)
> 
> Yeah, I have a "friend" who has gone a couple years with an empty cat
> and has passed emissions without a problem...
> 
> -Joe
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