[Vwdiesel] Limp Mode Frustration

Tue Mar 6 05:57:02 PST 2012

The rod can often still move freely for 95% of its travel, but stick
slightly as approaching the fully open position.  That results in an
overboost situation.  If you pulled the can and moved the lever by hand to
the extent of it's travel, you would be able to feel it.  I don't know if
you'd be able to feel it with the can still attached due to the spring
resistance in the can masking any sticking.

On Mon, Mar 5, 2012 at 9:44 PM, Dave Cook <davevw at yahoo.com> wrote:

> Do do I infer correctly from your post that if the vanes were stuck, I
> would be able to feel it in the lever?  Said another way, am I correct in
> assuming that the rod would not move if the vanes were stuck?
>
>
> Dave Cook
>
>
> ________________________________
>  From: Andrew .Libby <libbybapa at gmail.com>
> To: Tad <tadc at europa.com>
> Cc: vwdiesel at vwfans.com
> Sent: Monday, March 5, 2012 7:49 PM
> Subject: Re: [Vwdiesel] Limp Mode Frustration
>
> Here's a link to my current design:
>
> http://www.vwdieselparts.com/forum/viewtopic.php?f=21&t=11042
>
> I've made a couple since that one, but the design hasn't changed because I
> can't see a way to make it better.  :-)
>
> Because my control links the accelerator pedal to the vane lever, with my
> foot I can feel any changes in the motion of the vanes.  Because I
> currently work from home, almost all of my driving has been taking my kid
> to school and getting them at the end of the day.  Flagstaff is COLD in the
> winter and most of those trips are cold engine runs where it doesn't even
> make it to normal operating temp.  I've noticed that after a couple/few
> weeks of that sometimes I get the slightest hint of sticking when the
> engine is cold.  It goes away within 30 seconds or so of running.  A decent
> longer drive will eliminate the sticking.  If I go on an extended highway
> cruise with a few grades, then it can be weeks/months before the vanes
> demonstrate any resistance at all.
>
> Andrew
>
> On Mon, Mar 5, 2012 at 10:12 AM, Tad <tadc at europa.com> wrote:
>
> > Andrew - not my car but I figure I'll chime in since I'm here:
> >
> > 16618 - Boost Pressure Regulation
> >            P0234 -
> > 35-00 - Limit Exceeded (Overboost Condition)
> > 16492 - Manifold / Barometric Pressure Sensor (G71) / (F96)
> >            P0108 -
> > 35-00 - Signal too High
> >
> > are the codes, thrown variably.
> >
> > I'm curious about your VNT controller - what do you use to control the
> > vanes?  Stepper motor?
> >
> > I'm also surprised at your comment about extended highway runs
> > removing all carbon.  Not arguing, just I've never heard that before.
> > Could you be more specific about that, like the duration, steepness,
> > aggressiveness of the run (WOT the whole way?)
> >
> > I wonder if injection timing might play a role as well - as I
> > understand it, retarded timing = higher EGTs, which would logically
> > tend to burn off the carbon more.
> >
> > One possible clue is the OP had a blown head gasket, which I think is
> > pretty rare for TDIs.  I wonder if that's a cause or effect of the
> > overboosting?
> >
> > On Sun, Mar 4, 2012 at 6:37 PM, Andrew .Libby <libbybapa at gmail.com>
> wrote:
> > > I don't have a lot of experience with the computer controlled VNTs, but
> > > have a lot of experience with mechanical controls I've designed/built
> and
> > > pretty much perfected.  In my experience, lots of cold engine short
> runs
> > > will tend to cause the vanes to stick.  Running the engine up to normal
> > > operating temp and then taking several trips up an extended highway
> grade
> > > will remove ALL the carbon from the vanes.  They can stick in any
> > position
> > > or even just be a bit sticky at one extent of the range of motion.  In
> > > other words, I have seen them stick only at the fully wide open
> position
> > or
> > > the fully closed position.  My latest mechanical control has been
> > fantastic
> > > and has kept the vanes free, but the stock vacuum actuator/control is
> far
> > > less accurate.
> > >
> > > WRT this specific thread, I will admit I haven't kept up on it.  I
> > haven't
> > > read through quite a few of the posts.  Is it tossing a code for
> > overboost?
> > >
> > > Andrew
> > >
> > > On Sun, Mar 4, 2012 at 7:06 PM, <LBaird119 at aol.com> wrote:
> > >
> > >>
> > >> In a message dated 3/4/2012 1:49:39 P.M. Pacific Standard Time,
> > >> davevw at yahoo.com writes:
> > >>
> > >> I have  heard of people having success blowing the vanes clean by
> > driving
> > >> it  hard.  Is this at all effective if it is in limp mode and the
> turbo
> > >> is shut down by the computer?  Do I need to keep restarting it to
> clear
> > >> limp mode (briefly...) or can I keep driving it hard to try to blow
> it
> > >> clean even though it is limping?
> > >>
> > >> Also, if the vanes are stuck  from crud, will the actuator rod move?
> I
> > was
> > >> under the impression it  wouldn't
> > >>
> > >>
> > >>   Andrew Libby is probably the resident VNT expert.  He'd likely  know
> > best
> > >> about what you might or might not do or expect, and what would fix
> it.
> > >>  I'd say that driving hot and hard won't hurt it.  Even in limp  mode,
> > the
> > >> turbo is working.  It may not be boosting all it should nor the  vanes
> > >> moving as you'd like but you can still blow some carbon out anyway.
> > Hard
> > >> and
> > >> higher rpm can indeed clean stuff out.  Don't know if it'll fix it
> but
> > it
> > >> shouldn't hurt.
> > >>    Loren
> > >> _______________________________________________
> > >> Vwdiesel mailing list
> > >> Vwdiesel at vwfans.com
> > >> http://www.audifans.com/mailman/listinfo/vwdiesel
> > >>
> > > _______________________________________________
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> > > Vwdiesel at vwfans.com
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> >
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