car smells bad when running

Fred Munro munrof at
Mon Jan 21 14:37:59 PST 2013


In addition to the items Kent mentioned, if the odour smells like rotten
eggs it could be a problem with the catalytic converter. The sulphur in
gasoline is normally oxidized to sulphur dioxide. If the catalytic converter
is defective or raw fuel is bring burned in the CAT in an oxygen-lean
environment, the sulphur can be emitted as hydrogen sulphide, which is the
compound that gives rotten eggs that characteristic perfume. Sometimes
switching to a different brand of gasoline with a lower sulphur content will
reduce the odour, but if the CAT is bad you may have to replace it.


Fred Munro
'97 S6

-----Original Message-----
From: quattro-bounces at [mailto:quattro-bounces at] On
Behalf Of Kent McLean
Sent: Monday, January 21, 2013 5:09 PM
To: quattro at
Cc: v8-list; doubldz at
Subject: Re: car smells bad when running

EllenO wrote:
> ... my car smells really bad when its running ...
> Dee
> 1990 Pearl V8q

It could be a few things:

1) Oil dripping from the engine onto the hot exhaust.  It's probably an
    old seal or maybe a sensor leaking.  When the car is parked, open the
    hood and see if it smells worse in the engine bay. You might even see
    smoke from where it's hitting the exhaust.

2) Antifreeze. This wold be a sweeter smell. If it is stronger inside
    the car than in the engine bay, it might be the heater core leaking.
    Look for a wet, sticky spot in the front floor wells. The heater
    core is up inside the dash and is 8+ hours of labor to get to and

3) If the car has been parked for a while, don't discount a dead mouse
    that made its home inside the ventilation system.  Stick you finger
    in the coolant overflow tank and smell it. Pull the oil dipstick and
    smell it.  If your bad smell isn't one of those, it might be a dead

I CC'd the V8 list as they may have more insight.

Kent McLean
Audi-less for the first time since Bad Puppy.
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