Re: BOUNCE quattro@coimbra.ans.net: Admin request (fwd)

[raf40@oes.amdahl.com (Richard Funnell)]

Clarke,

I don't know enough about that model to be sure, but the symptoms you
describe are somewhat similar to what I've experienced with my urQ.  On the
urQ, the ECU goes into a limp-home mode when it believes there are problems
with any of its inputs.  Limp-home mode on my car is a hard cutoff at 4000
rpm.  Predictably for an urQ, the dealer I used to use knew nothing about
this.

If this is what your ECU is doing, it could be a sensor which is normally
within range until you get on the road.  I don't have the list for my car
with me, but I recall items such as the water temp sender, air temp sender,
over-boost and bad grounds being capable of causing this.

I would start by confirming that your ECU has such a limp-home mode.  If it
does, go through each of its inputs and ensure they're healthy.  Check
battery and ground connections as well, including the engine ground since
that affects the sender value as seen by the ECU.

If all else fails, you can (and I'm not recommending this) bypass the feed
to the fuel pump so that it is hot even when the ECU shuts it off (which is
what I assume is happening).  If you do go this route, I suggest using a
relay triggered by the alternator feed to the idiot light.  That way, the
ECU is in control except when the engine is at operating speed.  This is
important for safety reasons.  You would, however, be a lot better off
finding out the real problem.

Good luck.

>Apparently majordomo also traps requests for 'assistance' in the first
>few lines...
>
>| Dan |
>---
>Forwarded message:
>To: quattro@coimbra.ans.net
>Subject: Help on 5000 CD Turbo
>
>
>     Hi folks;
>
>     Need help, 1986 Audi 5000 CD Turbo, will go to 3800 rpm and then
>     closes down, like someone reached over and turned the key off.
>
>     The weird thing is that the car not moving, in the garage, or parking
>     lot, in neutral, will rev to 6500 with out hesitation
>
>     The knock sensor has been changed.  There are no faults showing on the
>     computer analysis.
>
>     This is the first time in 22 years, that the Audi/VW mechanic who is
>     working on it, has ever thrown up his hands in discuss (while I have
>     been around him anyway). Any ideas?
>
>     Clarke Paynter
>     Halifax, Nova Scotia, Canada
>     paynter@cibc.ca

Richard Funnell,
San Jose, California
'83 urQ
'87 560 SL