[s-cars] Mystery Miss

[Bob Rossato]

Bob,

I have developed the same exact misfire.  I first noticed it about a month
and 1/2 ago when I came back from a business trip.  The car had sat for a
week and when I first started it up upon my return it ran rough.  Sounded
like it was on 4 cylinders.  Revved it up and it continued misfiring, but
after a minute or so it smoothed out.  No problems while driving.  Strong as
bull.

Two or three weeks later it happened again after having sat unused for 4-5
days.  Same situation.  Clears up after a minute, then no more problems.  If
I drive it daily it never gives me a problem.  Let it sit for 4-5 days and
it will misfire at start up.

This past Sat morning I tried to isolate it by pulling injectors but it
cleared up by the time I was able to go through all five injectors.  I did
pull codes after that and got a "Fuel Injector for Cylinder 2 - Open or
Short to Ground - Intermittent" error code.  I assumed it was because I
pulled the injectors while it was running, but because I only got it for
cylinder 2 instead of all 5 (or at least more than 1) I thought this was a
possible lead.  Reset codes.

Fast forward to today and your post prompted me to go try it again as I
hadn't driven the car all week.  This time I set up VAG-COM prior to
starting it so that I could see if it would throw the injector code again
when I started it.  It ran rough again as expected, but alas, no codes other
than the CPS code, which was expected as I was checking codes prior to
starting the engine.

I was talking to Tom Mullane about it Saturday.  One theory he had was a
fuel pressure/vapor lock possibility that takes a while to clear up, but we
were a bit perplexed by why it would occur on a middle cylinder rather than
an end one.  But based on tonight's trial the Cyl # 2 code may have been a
red herring.

Anyway, no answers for ya other than to say "me too".  Maybe it's a Bob
thing.  I'm going to let it sit for a while again and see if I can isolate
the cylinder at least.

If you figure it out let me know.

Oh, for what it's worth, my car has 77k miles on it, plugs have about 40k on
them, and the plugs and boots looked good with the exception that the boot
on # 5 had the end lip torn off.  No oil in the spark plug wells.

Bob

> -----Original Message-----
> From: s-car-list-bounces at audifans.com
> [mailto:s-car-list-bounces at audifans.com]On Behalf Of Robert Myers
> Sent: Wednesday, September 29, 2004 9:34 PM
> To: s-car-list at audifans.com
> Subject: [s-cars] Mystery Miss
>
>
>
> Hi Y'all,
>
> Thanks to all who responded about my son's dealings with his
> Mercyless Benz
> stealer.  Apparently contacting the corporate offices helped.  He finally
> has his car back from the stealer.  Now on to the topic of this post.
>
> My '95 urS6 (RS2ed) has developed a mystery miss.
>
> It happens only when the engine is stone cold.  It disappears after the
> engine has run for less than two minutes and does not come back until the
> next time the engine is stone cold.
>
> FWIW, I have localized the miss to cylinder #4.
>
> I have pretty much ruled out a fault with the PSO since the miss
> disappears
> after the engine has warmed up a bit.
>
> I don't think it is a problem with a weak coil because there is
> absolutely
> no miss at high boost which is when a weak coil would show up.
>
> I put new plugs in about a week ago so that shouldn't be the
> problem.  Performance is superb after the engine warms up.
>
> Plug boots are reasonably fresh.
>
> The wires to/from the coils have been freshly reinsulated with shrink
> wrap.  I am pretty confident that I did this job correctly.
>
> What in the name of the Audi gods remains?  Any ideas?
>
>
> Bob
> Random Bushism: "A tax cut is really one of the anecdotes to
> coming out of
> an economic illness." George W. Bush, on The Edge With Paula Zahn, Sept.
> 18, 2000
> _____
> Robert Myers   304-574-2372
> Fayetteville, WV
> '95 urS6  Cashmere Grey
> _____
>