[Vwdiesel] 01 Golf TDi TURBO issues

[Tad]

If they weren't able to actuate the N75, that sounds like a prime candidate.


If your actuator was frozen, could be that the internal VNT mechanism is
clogged with soot.

Easiest cheapest would be the N75, so I guess start there...  I understand
you can swap that with the other similar valve that controls the EGR for
testing purposes.

Also could be a vacuum system problem (leak), which would impact EGR and
boost control.  Lack of vacuum will cause boost neg deviation (the code you
have).

Check the large vacuum hoses from the vacuum pump closely for leaks.  Also
the plastic hard pipe going to the brake booster is prone to splitting in
ways that aren't obvious.

Maybe just throw a vacuum gauge on at an appropriate point and see if the
system is pulling vacuum.

Also - how did the shop know they weren't able to actuate N75?  Did the
software report it, or did it just not seem to be doing anything?  If
software, that's electrical and rules out the vacuum system, at least for
that part.

On Fri, Jul 2, 2010 at 1:13 PM, Rolf Pechukas <rbp at 4u2bu.org> wrote:

> hi gang
> continuing saga of my Golf's poor running issues (after an alternator
> replacement left the post-turbo pre-intake pipe disconnected for 30+ miles):
>
> I am in 'limp' mode
> current error codes - OBD2: P1556 (VW: 17956)
> turbo not boosting
>
> waste gate actuator was frozen/rusted, replaced a couple weeks ago
> this did NOT fix the issue - promptly re-entered limp mode
> (however, turbo DID seem to boost temporarily - first few miles, before
> limp mode)
>
> we DO have a known bad EGR valve - shop tested, does NOT hold vacuum
> EGR code thrown recently (P401 or 402, manager not sure which, but
> INSUFFICIENT flow)
> that code is currently NOT showing up in the scan, apparently b/c limp mode
> disables testing further downline
>
> beyond that, shop is guessing plugged intake, possible N75 valve problem,
> MAF valve, or something else...
> shop was NOT able to actuate N75 through VAG-COM, they weren't sure why
> possible communication problem with their V-C system (?)
>
> again, bear in mind pre-intake hard pipe WAS disconnected for 30+ miles of
> VERY poor running, barely drivable (and driven 'hard' by the alternator shop
> to try to 'reset' the computer, also driven several miles bumpy dirt roads
> by me, all with intake disconnected)
>
> is there anything you all think might have come in through the intake to
> disable the turbo during that time, or put me in limp mode?
> road dust into the intake or head? turbo spewing lube freely froze it up?
> etc
>
> any other line of inquiry I might follow? any suggestions for shop to
> check? what order to proceed?
>
> thoughts? thanks,
>
> Rolf in MA
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