[s-cars] Procedure for testing coil, hesitation under boost.

[James Murray (QB/EMC)]

Original post from Craig Cook, and a good test this is:

"

here is hopefully a quick and inexpensive test for your suspect coil.
Go to Canadian Tire and buy a adjustable spark tester. The one with
the thumb screw that you can manually adjust the gap with.@ $9.00

Lay the coil packs on the valve cover.
Disconnect the coils that aren't being tested.
Use a short plug wire and connect one end to the coil to be tested  and the
other end to the spark tester.
Adjust the spark tester to, I'll say start with the 0.020 gap size. This
will probably equate to  about 1/4 inch on the tester.
Get someone to crank the engine while observing spark.
There should be a nice blue, crisp sounding spark.
Proceed to test all coils to get a baseline as to the spark quality.
Then proceed to adjust the spark tester to a bigger gap while observing the
quality of the spark
After some time and patience you will notice that the spark will turn yellow
and will not have that crisp sound as the others.
Obviously this will be the bad coil.
On a side note you may also want to disconnect the injectors so as not to
load the converter up with raw petrol.

I use this test all the time it never fails. The reason the tester is so
effective is because you're dynamically testing the coil.
As you know when the spark plug is in the cylinder ,the spark has to under
extreme pressure try and ionize the gap.This puts extreme loads on the
igniton coil secondary circuit when your are under load/boost. This tester
will simulate this condition every time.
We have a $30,000 dollar ignition scope at work. I'll still trust this test
over that piece of equipment on any give day.

"

/Jamu.

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Tom Green
Sent: Thursday, August 19, 2004 10:39 AM
To: s-car-list at audifans.com; iravwaudiporsche at yahoo.com
Subject: Re: [s-cars] Procedure for testing coil, hesitation under
boost. 


Date: Tue, 17 Aug 2004 22:39:06 -0700 (PDT)
From: Ira Deere <iravwaudiporsche at yahoo.com>
Subject: [s-cars] Procedure for testing coil,  hesitation under boost.
To: S-CAR-List at audifans.com
Message-ID: <20040818053906.97060.qmail at web61004.mail.yahoo.com>
Content-Type: text/plain; charset=us-ascii



I've swapped out known good coils from '92 S4, hesitaton gone.  How do 
I trouble shoot coils to find the bad one.  I've checked resistance and 
all are the same.  The #5 coil has been replaced previously.  Thanks
Ira
'93 S4 for sale 6000

Ira,

I was hoping someone would give you a lead to a comprehensive 
proceedure for this problem.  I recommend checking the archives at 
audifans and even audiworld.  SJM autotechnic always has some good help 
also.  You could also call SJM also for technical advice (and parts).
I know of several owners that have wound up replacing all 5 coils, one 
at a time, while chasing this problem, and then replace both POS, and 
plugs and boots and never have a clue what the original problem was.
Sounds like the access to a good coil set has done a good job of 
troubleshooting for you.  You can examine your coil set under bright 
light and magnification, looking for shorts in the wiring, arcing at 
grounds, whitish deposits around bolts, black or white deposits on 
wiring, but much of this observation has been done in hindsight, the 
problem coil found by elimination, and then the telltale evidence 
found.
Megging the coils is the only test that I know of, and the difference 
can be small, or none, except under boost.  HTH

Tom '95 S6, in Knoxville, TN

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