[s-cars] Urgent.. UrS4 vibrates when turbo should kick in...

[mlp]

Ivan, I'm no electrical genius, but when you say your problem is
"intermittent" and "occurs under WOT" which I assume means boost, then yes
the statement "...coil is working or not..." is an over simplification of
coil function and failure.  

A coil, and for that matter plugs &/or rubber plug boots  in "tired"
distressed or poor condition may work fine at low or no boost, only to
falter under high load (boost) requirements.  

I.e., in my personal case, an older set of coils which worked with no
apparent problems at stock boost (15 to 18 psi) faltered under new software
etc. and hardware revisions which asked the turbo to turn up the wick a bit
to 24 ~ 28 psi.  Swap a coil pack set from a newer, lower mileage engine
solved the problem.  Brian Powell's spark device suggested that the #3
cylinder coil was substantially weaker than the other 4 coils, but they
weren't in perfect shape either vis-à-vis his experience with the kind of
spark a new coil could/would push across the tester gap.

HTH
mlp


>-----Original Message-----
>From: Ivan Demkovitch [mailto:idemkovitch at hotmail.com] 
>
>So, statement that "coil is working or not" from 
>http://www.audifans.com/twiki/bin/view/Audi/TestingForSpark
>is not correct? Like I said problem is intermittant. It 
>happens rarely now. 
>But under WOT acceleration I alsmost always have couple of "jerks".
>
>
>>From: "mlp" <mlped at qwest.net>
>>
>>Actually Joe, I believe Brian Powell has a rather interesting coil 
>>tester. Perhaps he will chime in with his methodology (I 
>>
>>?  http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=538
>>
>>although Brian's device was pretty trick in that it allowed the gap 
>>between the contacts to be progressively lengthened so that one could 
>>build a relative basis from coil to coil of spark/coil strength.  In 
>>fact it looks a lot like the device in photo #2 at
>
>	http://tinyurl.com/75h3o  or
>
>	http://tinyurl.com/9yh7m
>
>Ain't the net amazing?
>