[Biturbos4] intermittant boost issue at high boost

alan cordeiro alancordeiro at comcast.net
Wed Dec 15 09:05:06 PST 2010


I was able to fix the problem very simply....I noted that inspite of the 
ever present _P300, multiple cylinder misfire.....cyl #5 and #2 would also 
come up occasionally as well (P305 and P302). That was all it needed to fix 
the problem....

So now I have a freshly delivered pair of EGT sensors from ECS tuning...I 
can return them and pay a 15% re-stocking, unless someone is interested in 
taking them off my hands....$275? for the pair

Thanks for all the help,

Alan

----- Original Message ----- 
From: "alan cordeiro" <alancordeiro at comcast.net>
To: "David Pramanik" <dap128 at hotmail.com>; <biturbos4 at audifans.com>
Sent: Wednesday, July 07, 2010 7:10 PM
Subject: Re: [Biturbos4] testing testing trying to post....


> 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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