[s-cars] help with a suspected bad coil.

[Paul Gailus]

Using a spark gap tester like Chris describes is a good idea.
I would also recommend that you put some spark plugs into the
connectors on the other 4 coils that you aren't testing, and then
ground the plug shells to the coil pack cover.
That way you will limit the maximum voltage on these other coil
outputs to a very safe value. Otherwise, it's possible that you could
overstress these other coils.
Any old plugs that will fit into the connectors will do.

You might also consider pulling all the injector connectors during the test
to prevent oil dilution, etc.

Paul

-----Original Message-----
>From: chris chambers <fastscirocco_2000 at yahoo.com>
>Sent: Jul 26, 2006 11:08 PM
>To: james McCarthy <jjssmccarthy at yahoo.com>, Scar <s-car-list at audifans.com>
>Subject: Re: [s-cars] help with a suspected bad coil.
>
>James,
>
>This is what I did, FYI this procedure does require a helper.
>
>Get an adjustable gao spark tester like this one, they are cheap:
>http://us.st11.yimg.com/us.st.yimg.com/I/sjdiscounttools_1907_54559075
>FYI I purchased mine at auto zone. 
>
>1. unbolt coil pack from engine
>2. position the coil pack so spark plug connectors are pointed up,
>balanced on a piece of wood (wood is used for insulation)
>3. Attach the clip to a good ground (I used a suitably thick piece of
>wire to attach to my ground point and then clipped the clip to the
>wire, this way I could unclip the wire and adjust the gap easier)
>4. Press the other end of the tester into the spark plug boot 
>5. Have your helper turn over the engine while you observe and confirm
>there was a spark. 
>6. Move spark tester to next cylinder and repeat test, after confirming
>each of the 5 cylinders all have spark increase the gap on the tester
>and retest each cylinder. 
>7. Keep repeating this test until you get a cylinder that fails while
>the others still have spark, you have identified the weak coil.
>
>
>HTH
>
>Chris
>
>
>
>
>--- james McCarthy <jjssmccarthy at yahoo.com> wrote:
>
>> Ok folks - could use some help.  The sedan (95.5) has
>> developed a stumble - at idle and through all range of
>> rmp.
>> I'm pretty sure it's a coil.  Here's why...
>> new plugs (1 week)
>> new plug boots (24hrs) 
>> swapped new pos in both slots - no change...
>> so tonight I pulled the coil harness (all 5 coils and
>> the cover) out of the avant (also a 95.5) and stuck in
>> in the sedan - stumble is gone.
>> So got to be the coils right?
>> But when I unplug the injectors one by one -  all seem
>> to degrade performance. So I suspect a coil is just
>> mostly dead - notcompletely.  How do I figure out
>> which coil is dying???
>> For what it;s worth the sedan is running stock
>> software with a FMIC and stromung exhaust.
>> TIA
>> -jamie in houston
>> 
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>
>
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>
>
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