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Discussion Starter #1
Hi. I have a 2001 Golf TDi that is currently having trouble and is periodically going into limp mode. The trouble codes that I pulled out of the car are P0402 EGR excessive flow, P0234 Turbo/supercharger overboost.

I started having the problem after I let the car idle for way too long in the cold as I was being a pansy and tired of freezing on my way to work. The temp was -20C, and all the way to work the car was warm but had no boost at all (I think, virtually no power). After sitting, the car worked fine all the way home (10-15 km of city driving). She had trouble next on the hiway after getting warm, the temp was -15C, after 15-20 minutes she suddenly stopped having power while passing someone. On the way home again, she was fine for 5-10 minutes then no power again.

I suspect that either the N75 valve or the VNT mechanism is sticky. For the particulars of my car:
- Intake cleaning at 270,000km,
- EGR blockoff at 270,000 km
- Intercooler removal and clean same time as well as crankcase breather catch can (still exhausts into intake but after the catch can)
- cold weather front
- Panzer plate

I am trying to watch the how to on the VNT cleaning procedure, have yet to recheck to see that the mechanism works with the mityvac as I did when I was cleaning the intake manifold. I also have a trouble code of P0380 Glow plug/heater circuit A that I think is most likely another glow plug harness.


Also curious about how to pressure check the TDi cooling system - is there any way to do it without the VW specific adaptor that nobody near me has?

Thanks,
Ryan - usually a Yamaha tech but today a diesel guy
 

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Strange that power would return suddenly and then go back limp. Normally limp mode pulls power and doesn't give it back until you shut the engine off and back on.

Your suspicious are possible. Also vacuum lines/system - it could cause the VNT mechanism malfunction and EGR problem.

The Autozone rentals will not work on the TDI coolant tank. You need an adapter :)
 

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Discussion Starter #3
I checked the vacuum lines and they are all still good but the arm for the VNT mechanism looks to be a little sticky. Also, I pulled off the charge hoses from the other side and tried spinning the turbo by hand. It feels a little sluggish like there is drag on it.

Is it possible that the turbine wheel would have buildup around it that causes it to drag? Or am I most likely looking at a bearing that was scrubbed from my long idling session (45 minutes or so in the cold).

The rod that moves the VNT seems to be able to move back and forth quite a bit on the actuator arm - is this normal?

The limp mode didn't shut off until the ignition was turned off, with the exception of when it initiated on the highway. The car stopped accelerating; it felt like a switch had been flipped and all of a sudden I was driving a slug. The acceleration was slow but not as slow as it was on the first day on the way to work. I checked the intake and there is oil from the breather still even with the crankcase breather catch can. Apparently I needed to vent it to atmosphere instead of still using the ccv input in the intake hose...
 
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