Loss of boost - any ideas?

[delaxm]

Driving along at constant throttle & the boost just drops off with a slight increase in exhaust note, switch ignition off & on makes it go back to normal - is this stcky VNT control vanes issue?
Car is 130pd Ibiza 2004 model with hybrid & remap, its done this once or twice in the past but did it 6 times in 4 miles today after being stuck in slow moving traffic.

 

[sssstew]

get vag com on it and see what its doing. When you say constant throttle, is this light throttle, mid or full throttle?

But first thing is to see whats logged.

 

[allen1020_0]

boost

Just had the same on mine. It was the turbo on mine.
My local vag bloke striped the turbo and cleaned it. It goes like stink now.

 

[devonutopia]

Can be the turbo. Also symptom of a split in a vacuum hose.

 

[delaxm]

Right, apart from the EGR codes (that are logged because I don't have an EGR) I'm getting 17964 charge pressure control Negative deviation P1556-35-10 intermitant.
Does the negative mean 'below zero' (as in knackered sensor) or below what it expected to see? (as in sticky VNT not giving enough boost)

 

[Aguilo]

Did you checked the N75 boost solenoid?

 

[sssstew]

negative means that its getting less that it wants in boost, ie probably a split hose, or bad joint.

Positive deviation is usually sticky turbo vanes as it cannot close the vanes fast enough.

re Aguilos comment above, the 130 PDs dont have seperate N75 valves, they have one large black vacuum control box at the back left of the engine bay.

 

[delaxm]

Problem found!

Been chasing a suspected boost leak for weeks now & finally traced it today to the pipe that runs under the drivers side headlight to the intercooler, it had a horizontal split in it about 50mm long - anyone had this before?

 

[S3 AKR]

You must be well chuffed to have finally found that one!! Its a nightmare when you know theres a problem and you can't find it. What car is it on ?

 

[delaxm]

Sorry should have said - 53 plate Ibiza 130 PD with hybrid & larger intercooler so some non standard pipework, the clue was a slight bit of oil around the drivers side fog light!

 

[sssstew]

excellant, as i expected. good find