Stumbling at high boost

John Corbishley JCorbs at
Thu Sep 14 15:54:09 EDT 2000

Interesting Simon.  I had almost the identical experience the other day in
my '85, but in third gear at the magic 4200 rev mark.  I immediately went to
Scott Mockry's site which addresses this issue, albeit for an '83.
Strangely, while it did it twice that evening, there has been no hint of it
since, although Scott also indicates that his observations were also
intermittent.  The only other thing its been doing recently is difficulty in
starting, also intermittent.

I guess I'll try plugs and the temp sensor as a first step.  That cut out
when overtaking is potentially disastrous.

John Corbs

----- Original Message -----
From: SIMON HOLTBY <sholtby at>
To: <quattro at>
Sent: Thursday, September 14, 2000 2:19 PM
Subject: Stumbling at high boost

> I was driving in my car today and pulled out to overtake a car in a manner
> which other Ur owners will be familiar with ie you are passed and fadeing
> into the horizon before the other driver can blink. Anyway this time as I
> was along side  with my foot to the floor and at full boost  my car
> hesitated and I had to back off.
> The last time this happened I traced the problem to the spark plugs which
> I had not checked for some time and the gap was too large. The high boost
> was putting the spark out. I checked the plugs and they were OK so for
> some reason I decided to check the air intake temp sensor and found the
> connecting wires had crimps on them and looked in a bad way. I
> disconnected them and out of interest went for a test drive and found at
> low boost the car was backfireing/pinking etc.
> After cutting about half an inch of cable off I tried to solder the wires
> on but old copper cable does not solder well. I decided to try using
> Jenolite rust eater which is a type of acid normally used on bodywork and
> I found that the copper became quite shiney and it was the best fluxing
> agent I have ever used. The temperature sensor is an item which Audi have
> thought of a daft price and quattro'd it, about 120 gbp so I did not want
> to get it too hot. But not much heat was required to get the solder to
> run.
> The resistance of this sensor is low, around 25 ohms so good connections
> are critical for accurate ignition timeing.
> Anyway went for a drive again and the problem was solved.
> Sorry for going on but this may help someone with a similar problem.
> Simon Holtby
> '84 Urq
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