[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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