Re: V8 surge problems

[Randall Markarian <asenna@mtvernon1.accessus.net>]

Eliot Lim wrote:
> 
> > Today I took my 90 V8 to the dealer for a repair, it is also due for
> > its 90K service so I asked about the Ox sensor because I have
> > noticed the same exact symptoms that you have described.  They
> > explained that a bad Ox sensor would cause surging only at idle.
> > Therefore, this could not be the cause of the problem.  I tend to
> > believe them, because have you ever heard of a dealer *not* wanting
> > to perform a service!
> 
> the reason for this is because there are no official audi factory
> bulletins advising them of the problem.  if they went ahead and
> changed the OXS and did not fix the problem then they would be
> up s*** creek wouldn't they?
> 
> >  They explained that this problem is inherent
> > to the V8 and something that they have narrowed down to a
> > transmission software problem.  Since my car has the original
> > transmission software, possibly that could help?  Eliot might shed
> > some light on that.
> 
> that is crazy.  how could the software cause the surge?  the torque
> convertor is a fully mechanical device.. the electronics do nothing
> more than make shifting decisions.  this problem has nothing to do
> with shifting decisions.
> 
> my car had the problem before and after a complete transmission
> and transmission control unit swap.  the problem disappeared when
> the OXS was replaced.. it is pretty conclusive as far as i'm
> concerned.
> 
> if you looked at the exhaust layout of the V8 it is pretty nutty.
> the pipes coming in from each of the bank meet in a "H".  the OXS
> sits right on the horizontal bar of the "H".  most of the exhaust
> gases just go straight through the "vertical bars".  that's why
> the OXS is doing such a poor job.
> 
Sorry, I was just relaying the information that the dealership 
provided.  But, I did not say that it was absolutely correct or that 
I totally agree with it.  It was food for thought.  Still, I can 
agree with what they told me, that there is so much going on with 
the engine during acceleration (info from all sensors etc.) that it 
could be naive to think that the Ox sensor would correct the problem 
each and every time on every car.  When my V8 had its 60K service, 
it had surging before and after the service even though the sensor 
was replaced!  Either Audi happenned upon a really lousy design for 
the Ox sensor(possible), or it could be a multifactoral problem.

Also, I requested the Ox sensor change and they warned against it 
because it might not work, they had nothing to lose (and money to 
gain) by honoring my request.  Note also, the 92 or later V8's have 
not had this problem(according to the dealer).  Did they 
redesign/relocate the Ox sensor for 92?  Did they add a second one 
(as on the v6 cars)?

Lastly, anecdotal evidence does not cannot be used to reach a 
conclusion.  Only a controlled study would allow you to do that.  
Perhaps with all the early V8 owners in the group we could reach a 
consensus about this.  I'll tell you next weekif mine is fixed.

Randall C. Markarian

1990 V8 Quattro