[s-cars] S6 down with bad misfire (again)

[jpb3wvu at frontiernet.net]

FWIW....

I am a newbie to the S6 and also had an occasional misfire or
stumbling.  I have heard the POS and coils are susceptible on
these cars from this list and instantly assumed the worst,
thinking that my occasional stumble and miss under load was do
to one of the culprits above.  However being the tightwad I am
and not wanting or even really knowing how to pursue down the
path of fixing the POS and/or coils I simple started out with
the simplest thing I could think of that could be causing the
problem.  I put in new spark plugs 3 weeks ago and have been
trying in vain to get the stumble to re-appear, but it hasn't
and I have driven around 1000 miles since the switch.  It seems
as though it was the plugs afterall!  When changing them I
noticed discoloration of the porcelain(sp?) aroud the base of
the plug but the tips looked worn but still had a good color
etc... and I thought that they couldn't possibly be the problem
but it seems as thought they were.  If you haven't changes ALL
the plugs in awhile that is where I would start.

If you have or know more about this ignition system than I do
please disregard this post and good luck!

john

> ----- Message from antoniodrummond at hotmail.com ---------
>     Date: Thu, 23 Sep 2004 03:55:31 -0300
>     From: ACD <antoniodrummond at hotmail.com>
> Reply-To: ACD <antoniodrummond at hotmail.com>
>  Subject: [s-cars] S6 down with bad misfire (again)
>       To: s-car-list at audifans.com
>
> First time around I thought I had a bad tank of gas: light
> misfire that would desapear and come back in a day or two. It
> got worse quickly and I began my search for culprits. After
> reading all the available tips I discarded POS failure and
> declared #4 ignition coil officialy dead. After I replaced the
> problem seemed to be gone... for 10 miles. I popped the hood
> again e began playing with POS and connectors, and cleaned the
> connectors with fine sandpaper. Problem was finally gone. If
> coil was the problem, why ithe misfire returned 20 minutes
> after replacing it? And why it went away after cleaning the
> contacts? Dirts could be causing intermittent misfire? Very
> strange...
>
> Two months of pure joy went by and - you guessed it - same
> thing happened again. I disconnected injetors one by one,
> problem was located at cylinder #3. I swapped the POS, no
> change. Checked the spark on plug: on first try, OK. Five
> minutes later, no spark. Nothing.
>
> I've been driving my car hard on the road - no track work -
> and temperature here is always between 80-90F. I can feel the
> heat coming from the engine bay thru the vent system. FMIC is
> on the way, hope it helps to control all this heat. Also will
> work on the heat sink and extra ventilation for POS. A simple
> flexible plastic hose with a filter to avoid water should do
> it. We can also connect the hose to a heat sink and cool the
> POS indirectly, avoiding moisture. I'll post whatever I come
> up with.
>
> I'm still investigating before replacing another ignition
> coil. Suggestions are welcomed.
>
> Antonio
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> ----- End message from antoniodrummond at hotmail.com -----