Turbo intermittent tdi 130

[caldirun]

Been having turbo trouble for a few days, no fault codes, turbo test works fine its when I am driving the car the problems occur.
I drive up a slight incline, smoke (grey I think) belches out and power is surging on and off.
I have changed the injector wiring loom as it seemed to be giving me the effects of a failling loom.
I removed the plug from the MAP sensor (could not swap it as the Passat 100 MAP is a different diameter) and it is smooth but turbo is not called in at all.
I changed the MAF (from my 100 Passat), still the same.
I have pulled over when it is giving problems and there is no vacuum on the actuator pipe at tickover, a quick inspection on vac lines and all seems well.
I think it maybe electrical as I have been having problems with interior lights and door switches, reversing sensors etc, is it likley to effect the N75 feed?

[Gary03]

I think it maybe electrical as I have been having problems with interior lights and door switches, reversing sensors etc, is it likley to effect the N75 feed?

I wouldn't have thought so as the N75 feed would come from the ECU whereas the interior stuff will be care of the CCM.
Like you say, there should be vacuum at the end of the actuator pipe when its at idle. Under normal operation, you should see the actuator arm drop back down when you pull off that pipe whilst the engine is ticking over.
It sounds to me like an intermittent fault with the N75 valve or its feed. Try another N75 first I reckon. Another test you could do is pull off the vac pipe from the take off on the servo vac pipe.
Suck the end of that small vac pipe. If all is well, you should not be able to suck air through it.

[caldirun]

Swapped the N75 from my Passat 100 still getting surging and clouds of smoke but works perfectly on the drive when I do a turbo test.
I have soot around the flexi that connects the cat, I am wondering if it could be blowing badly when driven causing the back pressure on the turbine
to fluctuate and making it rev too fast, over pressurise the intake, making the ECU drop the control rod to shut the vanes.
Has anyone had experience of this flexi leaking badly, if so did it effect the running of the engine?

[martin1810]

Use vcds to plot a turbo boost curve through the rev range. Wide open throttle 2nd & third gear. Check actual against required boost on your curve.

[caldirun]

Thanks for the reply, I did a log, the readings were all over the place, Map sensor made no difference so I removed the inlet pipe to the turbo
to check the play in the shaft. I noticed oil on the back of the lock carrier and on close inspection noticed that the turbo outlet pipe was split.
TPS wanted £100 + VAT for a 300mm x 50mm rubber hose, bought one off Ebay for £21.49.

update
New hose fitted and it is back to normal, I had to cut the old hose off at the lower joint and chisel the aluminium fitting out as it was very corroded into the steel pipe.