[V8] Gearbox/cruisecontrol/air recirc problem

[Jeremy Ward]

Pete,

Steve did an excellent write-up last September (our archives no longer
go back that far, so I have pasted his response below).

Sounds like you have a vacuum leak to me.

Good luck in troubleshooting.

Cheers,

- Jeremy

BTW, gas tank 'woosh' sounds normal to me, but it's been a while since I
have pumped my own gas (Oregon law, one of very few States here that has
this law)

-----------------

On every Audi other than the V8 I've been able to fix the CC with simple
measures ... adjusting the pedal switches or repairing vacuum leaks ...
that's still the first place to start IMO.  You only have one switch on
the automatic ... on the brake pedal.  Make sure that the switch
protrudes enough so that the pad that senses the pedal is fully
depressed against the switch body when the pedal is released.

I've seen problems with integrity of the vacuum system that drives the
actuator.  If you pull the vacuum line from the pump and apply a vacuum
there you should observe the throttle actuator motor get pulled in.  If
you don't have a vacuum pump you can depress the actuator motor and then
pinch off the end that attaches to the pump and the actuator should
remain in position when released.  If you do not find this to be the
case ... check to see that the pedal switch isn't leaking (IME a sign of
a need for
adjustment) or look for a broken "T" fitting in the system near the CC
actuator.  Of course, check that the linkage rod is attached to the
throttle body linkage while you are doing this.  Unfortunately most of
this stuff is buried behind the engine on the left side.

There is another bizarre possibility which you may want to investigate
... the CC uses the "hot" side of the brake light circuit to get its
ground.  It is a fail safe measure, that way when the brake lights come
on the CC is guaranteed to lose its ground.  If you lose all your brake
lights the CC will stop working too ... check to make sure that the
brake lights are functional.

One other peculiarity of the automatics is that the CC power is enabled
by the tranny computer, so if you have any tranny codes it may disable
the CC ... read out tranny codes and get them cleared.

Now ... to what I found on my car ... None of the simple stuff solved it
so I followed the troubleshooting guide in the book.  I found the ON/OFF
switch was bad ... I replaced it and the car now has CC.  Given your
situation, if you suspect that the problem is due to a bad switch or the
tranny ECU you might want to install a temporary fix by supplying a
direct switched power connection to the Cruise Control system.  I do not
think there is a big risk to doing this ... I drive around with the CC
on most all of the time anyway ... If you want help in figuring this out
get back to me and I'll get the wiring diagram out and figure something
out ...

I've never had a situation where the vacuum actuator, vacuum pump or CC
controller has been the cause of a failure ...

I hope you have a very safe trip out and back ...

Steve Buchholz
San Jose,

-----Original Message-----
From: Peter Littlewood [mailto:littlepete at freeuk.co.uk] 
Sent: Monday, February 23, 2004 7:13 AM
To: v8 at audifans.com
Subject: [V8] Gearbox/cruisecontrol/air recirc problem

Hello 
Have had a problem for a while with the cruise control not working, this
packed up the same time as the air con recirculator button (which now
doesn't seem to do anything) 
I seem to remember someone else having similar problems a while back
(possibly relating to the auto transmision) if this jogs any memorys I'd
be grateful for any feed back.
My transmision did throw a selection wobbly about 20k ago but seems to
have sorted itself out.
One last question, is it normal for a vacuum to form in the fuel tank
when running low on petrol? Often get a wooshing sound when I undo the
cap.

Thanks for reading

Pete Littlewood
1990V8Q   P.T
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