[Vwdiesel] Limp Mode Frustration

[Tad]

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
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