plastic distributor gear? Updated

[Mike Sylvester]

Is the mis-fire really rpm related or is it boost related?
If it is boost related, it could be a weak coil or bad plugs.

As far as the missing tooth...
The ECU uses the teeth to keep track of the position crankshaft
throughout the cycle.
That is what the engine speed sensor is doing.
If a flywheel tooth is missing, the the ECU will mis-count and possibly
fire the spark late.
In degrees, it would be number of teeth/360.
The engine will still run since there is a timing reference pin which
restarts the count every revolution.

It is possible that the ECU does not use the the engine speed sensor
directly.
It may have the ability to filter out a missing pulse.

The missing tooth location will also effect the problem.
A tooth missing early in the cycle could effect all cylinders.
If the missing tooth is after the last cylinder fires, then it would
have no effect at all.

However, I have no direct knowledge if a missing tooth will actually
cause a running issue.


Mike Sylvester

www.urq20v.com

> -------- Original Message --------
> Subject: RE: plastic distributor gear? Updated
> From: "gbs" <gschesel at comcast.net>
> Date: Thu, August 05, 2010 8:17 am
> To: "'gbs'" <gschesel at comcast.net>, "'200q20V mailing list'"
> <200q20v at audifans.com>
> Cc: gschesel at q.com
> 
> 
> DTC Codes pulled, just one stored; extended cranking times issue has been
> resolved; engine speed sensor replaced per the DTC.  
> 
> Still have severe misfire above 2500 RPM.  ???  No additional codes.
> Technician mentioned finding [just one] broken tooth on the flywheel.  Is
> that significant?  
> 
> The distributor replacement is pending, it still had the plastic gear.  But
> it's replacement is not expected to clear the misfire issue.
> 
> Question: isn't broken teeth on flywheel a cause of running problems?  I
> just seem to recall a verbal discussion not long ago with another 200 20V
> owner from this area, who successfully diagnosed and resolved an issue he
> was having and mentioned broken teeth on flywheel.
> 
> Thanks
> Gordy in St Paul
> > -----Original Message-----
> > Subject: plastic distributor gear?
> > 
> > 
> > I have my 200 in the shop due to severe misfire above 2500 RPM.  This
> > started happening on Friday a week ago, driving home from work after long
> > engine cranking period.  I had to kind of limp home, just 12 miles, using
> > highest gear and lowest RPMs.  Vehicle has "only" 123k miles; acquired in
> > late 2002 with 97,000, so you can see I keep it in the garage a lot and
> > drive mostly during summers as an alternate vehicle.  And it has been
> > experiencing very uncharacteristic extended cranking times this season.
> > 
> > My non-audi techs have not been able to find the problem, don't know what
> > to
> > look for, plus they do not have a way of pulling codes without an OBDI
> > diagnostic meter.  So far they have not removed the distributor to examine
> > the gear condition.  I'm thinking they don't want to end up billing me for
> > extensive diagnostic time due to uncertainty on what to look for.  They
> > are
> > being considerate knowing they have not worked on anything like a 200 20V
> > with CIS.
> > 
> > Should I assume a bad distributor and tell them to proceed with sourcing
> > one
> > at the prevailing part cost, probably close to $300?  (I see there is/was
> > one in marketplace for half that).  I'm not concerned about the part cost.
> > Just want to get at the correct solution.
> > 
> > Thanks
> > Gordy Schesel
> > St Paul
> > 200 20V Avant, Pearl, 123k miles
> > '91 100 10V Quattro sedan, 273k miles
> > '05 allroad, 2.7T, 77.5k miles
> > '96 Ford Conversion Van, 145k miles
> > 
> > 
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