N75 TEST ?

[swarcup]

Can anyone tell me if its possible to test the N75 valve, i have a hesitation on the Boost just as the pressure is starting to build just for a split second it looses it and then seems to come back but phasing in and out. Its as if it cant hold a certain boost pressure. I have changed all of the vac pipes and given it a scan on vcds but no fault codes related to the engine are stored. Can you test the N75 or is it just a change and chance that its the correct part. I have also blanked off the egr and disconnected the vac pipe and plugged it. Engine is a 2.5 tdi AKE. Looking at this diagram what else could it be apart from the N75 or the 2 pressure convertors. Any help would be much appreciated

 

[Mike.M]

Vcds output test or use basic settings.

 

[swarcup]

Tell me more.... i have access to vag com but arnt very experienced on it. If you could point me in a direction il get there

 

[adamss24]

Basic settings block 11 in the engine should cycle the N75 output on and off. Watch the VNT actuator is moving fully from full boost to min boost. I will also suggest you take the turbo off and check the hotside for foreign body damage, the early exhaust manifolds are known to break internally and send small pieces of metal into the turbo and VNT mechanism damaging them in the process !

 

[quattrodave]

Had a similar problem last week on my bau 2.5 TDI quattro. A small hose had split leading to the black/white non return valve on the bulkhead. Erratic boost and 'barking' engine with loss of power. No vcds codes either. Check your vac lines over.

 

[quattrodave]

Also forgot to say, check black/white valve only flows air one way

 

[swarcup]

Will dd thanks for the tip. All my vac lines are brand new so can eliminate that.

 

[swarcup]

Can anyone or does anyone know what the pressure should be for the turbo wastegate actuator, I will be connecting a mightyvac upto it tomorrow to check it to see if it holds the vacuum ok but thought i would check the operating pressure