[urq] intermittent ignition cutout, tach drops to zero

[Craig Cook]

I'll say it again, change the ignition module. Even if you have to borrow
one from a friend. It only takes a few minutes and it could solve allot of
headaches.
If that doesn't help solve the problem, then move on to more in depth
diagnostics.

Cheers,

Craig Cook.


----- Original Message ----- 
From: "Ed Kellock" <ekellock at gmail.com>
To: "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>; "Urq List"
<urq at audifans.com>
Sent: Wednesday, February 16, 2005 1:22 AM
Subject: Re: [urq] intermittent ignition cutout, tach drops to zero


> Hi Steve.
>
> Yes, engine still turning, car in gear, tach drops, power gone
> momentarily, then everything back on its own or definitely with a key
> off/on cycle.
>
> I don't think there's any correlation to temp as the temp here has
> been very cool and this can happen shortly after a cold start.
>
> Interesting though that you mention the ref sensors.  Some of the work
> I was doing was in that general area.  I will check those and their
> wiring for general condition, etc.
>
> Thanks!
>
> ----- Original Message ----- 
> From: "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>
> To: "Urq List" <urq at audifans.com>
> Sent: Tuesday, February 15, 2005 6:38 PM
> Subject: RE: [urq] intermittent ignition cutout, tach drops to zero
>
>
> ... sorry that I haven't been able to respond earlier ...
>
> Your indication that the tach drops to zero ... and I'm assuming that
> this means that the engine is still turning because the transmission
> is
> in gear and the car is coasting ... effectively you have lost power
> while the car is in motion.  I'm pretty skeptical that there is any
> connection between this and the vacuum work that you did.  The only
> complete WAG that might explain it would be if the ECU itself were
> locking up somehow ... but still I can't necessarily correlate this to
> the vacuum system work.
>
> I just went back and read the post that started the thread ... one
> thing
> that I'm wondering is whether or not there is any apparent correlation
> to temperature ... if so, I'd wonder if the issue isn't with the
> reference or speed sensors.  I would bet that you've already checked
> this, but is the Hall Effect Sensor timing set up correctly?  I
> suppose
> it could be marginal to the point where it might cause this ... but
> even
> that is a bit of a stretch.
>
> I wish I had copies of the wiring diagram for the car ... I know that
> there's an oddity in the ground reference between the ECU and the
> ignition driver module.  I think some cars have a direct connection
> from
> the ECU to a ground on the coil driver while others have the
> connection
> left open.  Does anyone else remember this?  I think you can see it by
> looking at the similar circuits on the urq and the '85 4kSQ in the
> Bentley.
>
> No matter what, unless you happen to find one of these wrong you may
> need to instrument things up a bit to try to get more information
> about
> what is working and what isn't.
>
> One more thing ... I wanted to explore one of your other comments
> relating to the OXS Freq Valve ... you said that the OXS Freq Valve
> *started* working ... it should be buzzing any time the engine is
> running.  It sounds like  perhaps you triggered the diagnostic mode by
> closing the WOT switch at idle ... this forces the duty cycle to 50%
> ...
> IME this causes the idle speed to increase.  If you are sure that you
> did not trip the WOT switch, then perhaps there is a grounding issue
> between the ECU and the engine block.  There should be a single ground
> wire that attaches to the back of the intake manifold ... this
> establishes the reference for the signals the ECU uses to determine
> the
> engine parameters.
>
> ... wish I could be more definitive!  Good luck Ed!
> Steve B
> San Jose, CA (USA)
> >
> > Actually, my tach needle does not bounce around.  It drops to zero
> and
> > stays there until the power to the ignition comes back.  I do not
> > believe this is fuel related in any way.  My recent work had to do
> > with vacuum leaks and I merely wondered if there could possibly be
> any
> > connection, an intersection point of some sort in a single device
> that
> > has both vacuum and power input/outputs... the frequency valve
> maybe?
> _______________________________________________
> Audifans urq mailing list
> Send posts to: mailto:urq at audifans.com
> Manage your list connection:
> http://www.audifans.com/mailman/listinfo/urq
> Have an urq question?  Check the Audifans Knowledgebase!
> http://www.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all
> contributions welcome!
>
> _______________________________________________
> Audifans urq mailing list
> Send posts to: mailto:urq at audifans.com
> Manage your list connection: http://www.audifans.com/mailman/listinfo/urq
> Have an urq question?  Check the Audifans Knowledgebase!
> http://www.audi-quattro.org/cgi-bin/twiki/view/Audi/UrQuattro
> Have an urq answer? ... Please help others by adding to the KB ... all
contributions welcome!