[Biturbos4] testing testing trying to post....

Wed Dec 8 06:46:34 PST 2010

Even with no pressure on the gas pedal the throttle body lets a little
bit of air through to idle the motor.  I'm not sure how its done on this
drive-by-wire system, but many cars have an idle sensor on the throttle
body that lets a small amount of air bypass the butterfly valve so that
the engine can idle at a pre-programed rpm rate.

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-----Original Message-----
From: biturbos4-bounces at diablo.audifans.com
[mailto:biturbos4-bounces at diablo.audifans.com] On Behalf Of Steve Munk
Sent: Tuesday, December 07, 2010 10:43 PM
To: alan cordeiro
Cc: biturbos4 at audifans.com
Subject: Re: [Biturbos4] testing testing trying to post....

Hi Alan, 

I wouldn't count on the throttle butterfly creating anything close to an
air-tight seal. Best to disconnect the throttle body and seal the pipe
at that end too.

Steve
--
Steve Munk                           http://people.arsc.edu/~munk/S4
HPC Systems Analyst                  '01 Audi S4 biturbo, silver 6-speed
Arctic Region Supercomputing Center  '01 Audi A6 2.7T, gold 6-speed
University of Alaska Fairbanks       mailto:stevemunk71 at gmail.com

On Jul 7, 2010, at 4:10 PM7/7/10, alan cordeiro wrote:

> Having recently found out that the 945 degrees C may not indicate bad
sensors, I thought perhaps there was a leak at 5 psi and beyond in the
pressurized part of the intake manifold system. To test for this, I
spent some time fabricating a set of hoses and adapters to pressurize
the intake manifold/plenum.
> 
> 1) Blocked off the main intake (coming from the MAF sensor to the Y
pipe).
> 2) Removed the crankcase vent pipe, and added in a pressure adapter
from my air compressor,
> 3) set the outlet pressure at 5-7  (hard to guess down so low),
connected the hose to the fitting.
> 
> Air is now going into the upper Y pipe, and should be pressurizing the
system, including turbos, up to the throttle body (where presumably the
butterfly valve should keep it from going further.
> 
> I now have a continuous air flow going into the intake, and there is a
rushing sound of air.......but pressure never builds up. I cannot find
where the air is going......if appears to be going into the engine.
Unlike my older Audi, I seem to have no way of knowing if the butterfly
valve is open or closed...is there some way to verify this?  I cannot
seem to find why so much air is vanishing, even at very low pressure,
since the pressure is never getting a chance to build up in the system.
> 
> Has anyone had this problem and overcome it?  The Bentley does not
give any hints...
> 
> Thanks,
> 
> Alan
> 
>  ----- Original Message ----- 
>  From: David Pramanik 
>  To: alancordeiro at comcast.net ; biturbos4 at audifans.com 
>  Sent: Monday, December 06, 2010 3:01 PM
>  Subject: RE: [Biturbos4] testing testing trying to post....
> 
> 
>  Alan,
> 
>  The EGT sensors on the 2.7T have an operating range of 945C to 1035C.
Under most driving conditions (your idling test included), exhaust gas
temperatures will be below 945C so the sensors will read their minimum
value 945C.  So what you are seeing isn't necessarily a problem.
> 
>  The problem is that when the sensors when they fail, they read 1035C.
This causes the ECU to think that exhaust gas temperatures are too high
and the ECU responds by significantly increasing the fuel injector pulse
width, which can cause stumbling or missing.  If you log with VCDS whil
the car is missing and see 1035C for the EGT values, it could be that
the EGTs are indeed faulty.
> 
>  But given how expensive the EGT sensors are, I wouldn't replace them
without doing more diagnosis.  Most often when I've seen missing under
boost, it is due to old or worn sparkplugs.  Simply swapping in fresh
plugs will typically alleviate the issue.  If that doesn't solve it, use
VCDS to pinpoint the cylinder(s) that are misfiring and swap the
coilpacks around to see if the misfiring moves with the coils
(indicating a faulty coil).  Baring that, you could have an injector
that is partially clogged or not responding properly.
> 
>  If you do find that the EGTs are infact faulty, they can be rather
tricky to replace.  You'll probably need to bend some 17mm wrenches in
order to be able to get a good angle on the sensors.
> 
>   VCDS is the closest thing to the VW/Audi factory diagnostic tool
(and in some cases, it has capabilities that the factory tool does not),
so it is well worth the money if you plan on owning and maintaining an
aging Audi.
> 
>  -Dave Pramanik
> 
>> From: alancordeiro at comcast.net
>> To: biturbos4 at audifans.com
>> Date: Sun, 5 Dec 2010 15:36:38 -0500
>> Subject: [Biturbos4] testing testing trying to post....
>> 
>> Good afternoon to all list members. Since I signed up November 5th,
it 
>> appears that all messages from the list have ended.....if indeed I am
the 
>> jinx who slowed the dribble to a full stop, I need to apologize.
>> 
>> If not, since a month has now passed with no message, I thought I
would 
>> create one to jump start it.
>> 
>> A brief introduction, my name is Alan Cordeiro, and I recently gave
up a ten 
>> year long ownership of a '91 200q with 285k miles and replaced it
with a 
>> 178k mile 2001 S4.
>> 
>> My original quattro vehicle was a 1986 5000CSq....and I have been a
list 
>> member of the original "quattro" list since 1995, from the days we
posted to 
>> quattro at swiss.net, (but gave it up to focus on the more specific
200q20v 
>> list, and now hopefully this list.
>> 
>> As with all previous cars, the current S4 is also performance
enhanced, 
>> including APR stage 3 chipped, RS4 turbos and clutch, piggie pipes,
3" dual 
>> inch exhaust, and Vogland coilovers.
>> 
>> I am looking for advice on two items:
>> 
>> 1) Having missing at high boost.......it would appear to be defective
EGT 
>> sensors. Using a friends VCDS, we noted both read 945 degrees C 
>> continuously, even with the engine idling. Does anyone know what made
them 
>> both go bad suddenly?
>> I have the set of two on order, and expect them in a few days. Please
give 
>> me any advice on how best to replace them.
>> 
>> 2) Considering buying a good diagnostic tool.....possibly a ROSS-TECH
VCDS, 
>> but wondering about all the other much cheaper tools appearing on
e-bay. 
>> Have anyone of you bought these? Do they work, and what is the
downside? The 
>> prices seem very attractive,
>> 
>> Thanks,
>> 
>> Alan Cordeiro
>> 
>> ----- Original Message ----- 
>> From: <biturbos4-request at www.audifans.com>
>> To: <alancordeiro at comcast.net>
>> Sent: Friday, November 05, 2010 9:01 PM
>> Subject: Welcome to the "Biturbos4" mailing list
>> 
>> 
>>> Welcome to the Biturbos4 at www.audifans.com mailing list! Welcome to
the
>>> Biturbo S4 List at audifans.com
>>> 
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