When I stripped and cleaned the turbo and inlet manifold in April I also replaced the vacuum tubing with new silicon tube from ebay. The engine stutters at about 2000RPM and goes into limp mode. The stutter suggests an air leak in the inlet circuit, according to my turbo tdi web site.

 

I checked and there are two sizes for the vacuum tubing 3.5mm and 5mm.

I used 3mm and 5mm.

The difference in cross sectional area between 3mm and 3.5mm is 26%.

My pressure calcs knowledge is not good but this suggests that the 3mm has upto 26% more vacuum pressure (if that makes sense) than the 3.5mm which may explain the above fault.

Potentially this may cause the actuator to open and close the turbo more than it should, hence limp mode.

 

The ad on ebay said for Skoda and I did not check it was correct.

I guess it is worth changing as I am stumped as to what else it may be.

Edited 2 September, 201510 yr by jackg

Wrong tree receiving barks, I fear.

 

The only difference a smaller cross-sectional area could make is slowing the rate of change of vacuum signals, not their steady-state values.

 

Surely the classic VNT mechanism clogging up is the more likely scenario? Edit: sorry, missed the first sentence somehow.