[s-cars] [s-ars] Stumbling under acceleration.....probable boost leak? Or...

Tom Green trgreen at comcast.net
Mon Nov 30 18:43:55 PST 2009

I have no issue with Dave's advice.  I think it is premature to  
abandon the original setup yet even if one coil has failed or is weak  
really, since it does work except under high boost.  Here is a link to  
a Dave Forgie post on the matter, and is the only reliable way to test  
coils that are only failing under high boost.  There is one
other method -- wait until it fails completely and hope it doesn't  
take out the ECU with it. : - )


There are some spark gap testers that are made for the coil on plug  
installation and make this easier.  The procedure is also in Bentley.   
Stop fuel flow, and lay the
plugs on the valve cover while attached to the coils and observe the  
spark at each plug looking for the weak spark.  Finding the weak coil  
is not a job I would take
to the Audi specialty shop or dealer -- perhaps a URS specialist that  
has done this before.  Because of the length of time required to fully  
troubleshoot and repair
this problem, the labor meter will really be spinning.  This is best  
done as a DIY project, and you do want to do it because you want to  
know what coil to discard if
you are going to sell the remainder or repair to use.  Unless you find  
the bad coil the entire pack will be useless to you or anyone else.

Some help from another owner would be helpful, if only to spin the  
starter.  The results may not be crystal clear and leave room for  
subjective opinion, since visually judging the spark quality is as  
much art as it is real science.   A good Model A mechanic could  
probably do this in a heartbeat.

This should help you understand why you want to eliminate everything  
else as a possible cause before starting on the coils.


> On Monday, November 30, 2009, Dave Dawson <djdawson2 at aol.com>  wrote
> Your question #3:
> That is the bitch about coil packs.  People can piss and moan all  
> they want to about 1.8 coil packs... but no matter how you look at  
> it, they save you a ton of money and frustration.  Plug and play...  
> swap one $20 coil with a new one and test.  Problem not solved...  
> swap the new one into the next cylinder.  Doing this with the OE  
> setup is impossible, as installing one new coil pack is a project by  
> itself.
> I would urge you to also replace the plug boots on your coils prior  
> to replacing any of them.  This is another common failure causing a  
> misfire under load/higher boost.
> Good luck,
> Dave
> -----Original Message-----
> From: Jim Fleischer <jim at almgt.com>
> To: s-car-list at audifans.com
> Sent: Mon, Nov 30, 2009 9:41 am
> Subject: [s-cars] Stumbling under acceleration.....probable boost  
> leak? Or...
> Hey guys,
> Thank you for all the responses to my stumbling issue......after a  
> long holiday
> week and a quick 1500 mile round trip t Eastern Kansas (not in the  
> S) I'm
> finally able to tart tracking down the issue.  Here's my plan of  
> attack.....
> 1.  Will build a leak tester and check for leaks in the intake  
> hoses.....
> 2.  If no leaks found, will check spark plugs and replace with NGK's  
> as
> suggested by Dave Dawson
> 3.  If that doesn't do it, then will go the coil pack route.  One  
> question,
> though.....if I am only experiencing issues at higher boost, but not  
> during
> normal idle, how can I tell when there is a "miss" at idle when  
> swapping out the
> coils?
> 4.  If that fails, well.....I guess I'll post again and see what you  
> all have to
> say before I, "gulp" take it to someone.....
> Thanks all....I'll let you know what I find in the days to come.....
> Best regards,
> Jim Fleischer
> '95 s6 avant
> '83 ur

More information about the S-CAR-List mailing list