[s-cars] Rough 'cold start' idle? & Revs drop when Air Con switched on?

[Paul Heneghan]

Cars of this age are beginning to suffer from perished rubber hoses - check
all the intake hoses - turbo models are particularly susceptible to bursting
the odd hose or three.

Idle stabiliser valves also start playing up at this sort of age and get
sticky - lots of carburettor cleaner can help.

O2 sensor is also high on the list - was it replaced at 80K miles?

Spark plugs?  They must be the correct large-cored platinum ones - Original
Equipment F5DPOR BOSCH PLATIN Electrode Spark Plugs.  They get replaced
every 20K miles or sooner if they are causing a misfire (usually under high
boost).

Multifunction temperature sensor - these are also notorious for failure

Before you start throwing money at the problems, you must pull the codes
from the ECU (http://www.sjmautotechnik.com/ecuf20v.html).  You may well
have a 234x code (O2 sensor problem).  Pulling codes can be done by the
dealer, a suitably equipped specialist or by you.

If you want to do read the codes yourself, then you need to get hold of a
good manual (Bentley on CD is probably your best bet at about $100 - Haynes
is next to useless for engine problems on these cars).  Reading the codes
can be done by installing an LED and dropper resistor (not fitted as
standard to UK models - at least not to 1995 S6 models), or you can get an
interface and a program for a PC (http://www.ross-tech.com/vag-com/ about
$200).  Read the archives for more information about these procedures.

Read Scott Mockry's superb web site on Audis
(http://www.sjmautotechnik.com/ - lots on 5 cylinder, 20 valve turbos).  In
particular read what he says about buying an old, high-mileage 20V turbo
(it's the bit in bold in the first paragraph in
http://www.sjmautotechnik.com/20vboost.html).

If you don't feel up to any of this, then remortgage your house, order a
special cheque book with extra wide boxes for the currency and toddle along
to the dealer!  Seriously, it might be worth getting the dealer to charge
you for the 30 minute's work involved in reading the codes and preparing an
estimate - then you can decide whether to take it further.  I don't know
what dealers charge these days - I haven't used them in over 10 years.

If you live near Kettering, you might like to get in touch with Phil Payne,
a freelance Audi turbo specialist - have a look at
http://www.isham-research.com/quattro/.

You could sell it to me in its present state for £500 - my wife needs to
replace her 100 Avant (10 valves, no quattro, no turbo, but well on the way
to 1/3 million miles!).

Good luck!  Let us know how you get on.

Paul
1995 S6 Avant (UK spec)

> From: Michael Wakefield <mwake at rmi.net>
>
> Our cars have a heater built into the oxygen sensor.  When the heater
> burns out (and they do), it takes a while for the sensor to get up to
> temperature and provide a signal to the MAF to adjust the mixture.
> This will make the engine run a little rough for a while.  I would
> start by checking the sensor heater.
> Mike Wakefield
>
> On Sunday, April 27, 2003, at 09:08 AM, Gary Bray wrote:
>
> > I've just started the 'initial sortout' on a recently purchased '92, UK
> > spec S4.
> >
> > x2 irritating problems .....
> >
> > [1] From cold she starts on the button but will not idle smoothly 'til
> > she begins to come up to temperature (a minute or two?).
> >
> > [2] At all times (most notable at idle), switch on the Air Con and
> > engine revs' drop 200/300RPM.
> >
> > Anyone hot on instant fixes?!
> >
> > Regards to all,
> >
> > Gary