[s-cars] S4 #4 cylinder miss

[Bob Frizzell]

Jim,
Are all the coil wires in good shape?  Check carefully - the covering gets
brittle and then they start to arc. If not that, it seems to me it must be
#4 coil.
Bob
93//S4
----- Original Message ----- 
From: <AUDIJIM at aol.com>
To: <quattro at audifans.com>; <Audi5TurboTech at yahoogroups.com>;
<urq at audifans.com>; <s-car-list at audifans.com>
Sent: Tuesday, November 15, 2005 8:08 PM
Subject: [s-cars] S4 #4 cylinder miss


> Hello,
>
> The patient is a 1993 Audi S4. Lehmann modified engine (lower compression)
> and Lehmann chipped. RS2 injectors, EM and Turbo. I have a definite miss
at
> cylinder #4. When the car is cold, it is running on 4 cylinders. As it
gets
> warmer, it gets a little better, but I still hear and feel a miss. It's at
it's
> worst when it is cold. I have not checked codes yet (VAG COM) but will
tomorrow.
> Pulling the connector off cyl. #4 fuel injector makes no change in the
rough
> running condition. Pulling the connectors off the other fuel injectors
make the
> engine run on 3 cylinders, so it is definitely #4 cylinder that is the
> problem. I swapped injectors from #4 to #3 and #3 to #4 and the dead
cylinder is
> still #4, so that eliminated the bad injector possibility. Compression
test is
> good at all cylinders, that eliminated any problems with the engine. I
> back-pinned the fuel injectors with an LED test light and confirmed the
injectors are
> getting and electrical signal to fire. Confirmed that fuel injectors work
by
> removing fuel rail with injector still attached, and tried starting car.
Equal
> spray pattern at all cylinders. I tried swapping POS with the connectors
to see
> if the cylinder would change location, #4 cyl. still has a miss. Changed
spark
> plugs, no change. Tried ECU from stock AAN, no change. Tried another set
of
> POS and still no change. I pulled the coil packs and inserted spark plugs,
> grounded against valve cover, cranked engine and found spark at all
cylinders.
> Reinstalled and I still have a miss at cylinder #4. Tomorrow I will
physically
> change coils from cyl. #4 to cyl. #5 and see if the miss goes to cyl. #5.
I
> followed the Audifans Knowledge (S4/S6) base about a miss in one cylinder,
but it
> was only a procedure on how to prolong the life of the POS that uses 2
> channels by swapping the wire to the bad coil to the unused portion of
that POS. That
> was no help. I realize that my spare parts engine (complete AAN running
great
> before it was removed from totaled car) is no guaranty that my spare parts
> are fault free. The previous owner on my S4 said that the problem is new
within
> two weeks or so. If anyone can help or has seen this before, I'd
appreciate
> your thoughts/help. I bought this car to replace my 285,550 mile 5000TQ
that
> needs a ton of work. Now I have two cars that need a ton of work.
Hopefully when
> I get home after work tomorrow (4 PM EST), I'll have a lot of help from
you
> guys on where to turn next.
>
> Thanks,
>
> Jim
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