[s-cars] Bad coil? coil testing question

[Bob Frizzell]

Chris,
Be sure to check the coil wires carefully.  The insulation gets brittle and
cracks and can cause arcing and the symptoms you describe.
Bob, too damn cold in Edmonton
93//S4

----- Original Message ----- 
From: "chris chambers" <fastscirocco_2000 at yahoo.com>
To: "Scar" <s-car-list at audifans.com>
Sent: Sunday, January 09, 2005 12:02 PM
Subject: [s-cars] Bad coil? coil testing question


> Gentz,
>
> I have a "miss" during hard boost pulls in 4th and 5th gear (haven't
> noticed it in others).
>
> Replaced the spark plug connectors which helped but it looks like a
> failing coil. I did some searching and read that you can check the coil
> by using an adjustable spark tester. Here is the test I found:
>
> "Here is hopefully a quick and inexpensive test for your suspect coil.
> Go buy an adjustable spark tester. Try to get one with the thumb screw
> that you can manually adjust the gap with. Cost is usually around $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.
>
> Searching the net I found a pic of an adjustable spark tester here:
> http://www.drivewerks.com/catalog/images/tools2003/THE-404.jpg
>
>
> So before I leap forward with blind faith I am wondering if anyone else
> has tested their coils in this fashion. I don't want to damage a good
> coil trying to determine if I have a bad coil.
>
> Also I have found coils at bimmerzone for ~ $124 ea...is there a better
> deal anyplace else?
>
>
> Advice?
> Thoughts?
>
>
> Thanks
> Chris
>
>
>
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