[s-cars] Momentary cut out under full boost

Tom Green trgreen at comcast.net
Sat Oct 27 12:59:12 PDT 2007

There have been enough failures of this sensor and resulting 0 speed  
reading on
the speedometer to tell that the failure has no effect on drivability  
of the car.  I used
GPS for an occasional speed check and even avoided a 88 mph citation  
in western
KS  after a little show and tell dance.  :-)  I didn't think those  
little ripples in the
landscape were enough to hide in much less attenuate radar signals.

My last encounter with those accommodating Kansas troopers was for a  
105 mph
infraction.  He swooped down from the man made obstacle created by  
the widely-
spaced interchanges and interrupted my journey in the Navy recruiting  
Chrysler convertible on a Sunday afternoon with not another vehicle  
in sight on the
interstate.  I agreed that yes, we were in a hurry for an appointment  
in Denver early
Monday, so he just cautioned me to drive carefully and sent us on our  
way.  That was
easy since that was about the top speed of the car and the distance  
between fuel
stops available could make you uncomfortable in that thirsty beast,  
so you didn't
pass up many on a Sunday in the early '70's.  :-)


-----Original Message-----
> Date: Sat, 27 Oct 2007 13:19:33 EDT
> From: FvAMI at aol.com
> Subject: Re: [s-cars] cars] Momentary cut out under full boost
> To: robert at s-cars.org
> Cc: atay at cox.net, s-car-list at audifans.com
> Message-ID: <cc2.1a58939a.3454cd25 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
> Robert,
> Yes, it could be a lot of things ... however a 0 Speed reading is not
> expected in any circumstance you described.
> Aaron informed me he believed the speed went to 0 before the  
> cutoff. Even if
> it happened during the cutoff that still is not correct.
> The speed sensor and connection may be the first place to look.
> I don't know what the ECU will do (if anything) if all of a sudden  
> it is
> producing 25 PSI of boost at 50 MPH and suddenly the speed (seen by  
> the ECU) drops
> to 0. But the Audi engineers may look at that as some type of serious
> situation and cut the fuel ... don't know ...
> Best regards,
> Feico van der Laan
> In a message dated 10/26/07 7:55:48 AM Pacific Daylight Time,
> robert at s-cars.org writes:
>> Or the ECU could be cutting ignition as a result of an input from
>> some source, either erroneous or correctly.  Ignition is cut in
>> response to a signal the ECU interprets as overboost or to a signal
>> the ECU interprets as engine rpms exceeding the rev limiter.
>> Overboost can be the result of any number of factors, not the least
>> of which, might be a split WG diaphragm or a faulty WGFV or a
>> blockage in the WGFV to WG hose.  Exceeding the rev limiter can
>> happen (in addition to actually over-revving the engine) as the
>> result of an improperly set limit in the ECU software.
>> Bob

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