[s-cars] No spark to #5cyl- help wanted

[matt ludwig.]

Just an update for everyone (that I meant to post 4 days ago) about  
this finally getting resolved. Use as data points or not....

It turns out the issue was very compounded and not simply just #5cyl  
as we suspected after Round 1 diag. It turns out:
- #5 coil pack was fine
- #5 injector fine
- swapped #5 coil with other POS, prob remained
- swapped in new POS w/ #4, 5, 5 channels on it- still bad
- #2 coil pack failing.... but sporadically
- #2 coil pack failing like this because of POS it was on was  
failing... thus killing the coil.... softly.
- Up inside #2 coil with flashlight, it is seen a crack in metal  
connector to plug is cracked... slightly

Solution:
- replace #2 coil
- Replace POS for #123 cyls

She pulls hard! : )

matt ludwig.
~~~~~~~~~~~~~~~~
1995.5 S6 Avant
South Portland, Maine


On Jan 8, 2009, at 7:56 PM, Paul Heneghan wrote:

> It would help enormously if you had access to another S6 to swap bits
> between them so you could eliminate components from your enquiries.   
> It's
> possible (though unlikely) that you have two faults - something like a
> failed plug and failed plug connector would allow you to change as  
> many
> other bits as you liked and still get no spark.
>
> From my (rather limited) experience, an intermittent misfire is  
> usually a
> problem with the HT side (coil, plug connector or plug), and a  
> permanent
> no-spark situation is usually a problem with the POS or the feed to  
> the POS.
> Really, you need to get an oscilloscope on the connection between  
> the POS
> and the coils and see if #5 looks different.  If there's no pulse to  
> be
> seen, then look at the signal on the primary of the POS.  If still  
> no pulse,
> then trace back to the ECU.
>
> I vaguely remember somebody talking about a shorted coil that kept  
> blowing a
> fuse somewhere near (or in?) the ECU
>
> Have a look at the following web page for lots of info about fault  
> finding
> misfires:
> http://forums.audiworld.com/s4s6/msgs/103391.phtml
>
> Also check out Scott Mockry's excellent page on S6 ignition at
> http://www.sjmautotechnik.com/trouble_shooting/S4_Ignition.htm
>
> With the help of that page I've fixed two POS problems and two coil
> problems.  It's worth getting hold of one of the spark plug  
> testers.  I had
> an intermittent misfire under load that turned out to be a weak  
> coil.  The
> spark could jump 6mm but couldn't jump 8mm.
>
> Good luck!
>
> Paul
> -----Original Message-----
> From: "matt ludwig." <urs6avant at gmail.com>
> Subject: [s-cars] No spark to #5cyl- help wanted
>
>> In short; the coil pack, POS and wire leading to the POS checked out
>> OK. Any thoughts?
>