How do you test the vacuum box to make sure it is working correctly?

[Harry1212]

I'm having an issue with my car at the moment, it overboosts and goes into limp mode, the only fault code that shows up is fault code 17965/P1557/005463 - Charge Pressure Control: Positive Deviation

 

it boosts as normal after turning the engine off and back on, usually goes into limp mode under load and i've seen boost on the gauge go as far as 2 bar on the standard turbo, the car has a "safe" standard map with low torque and boost has also been restricted to a safe amount on the map

 

I don't have sticky vanes, it's a brand new turbo and my previous turbo also did this which I removed thinking the turbo was faulty

 

done a full service recently and i always run BP Ultimate diesel

 

I want to now investigate the vacuum box to make sure it is working correctly, is there any way to do this, i've ordered some vacuum pipe off eBay which i'll be using to replace the pipes if i find any leaks in the pipes but before I do that is there any way to test the vacuum system? cheers

[SuperbTWM]

the car has a "safe" standard map

I get the feeling your trying to say that the car has had a moderate remap. A standard map would mean the car is stock.

[Breezy_Pete]

I would imagine swapping with one from a trouble-free car would be a good test?

[Harry1212]

I know a few people with vag com and other software so was more wondering if there was some sort of test that can be done to see if it is functioning ok

 

then i'd get all the pipes inspected and replace the entire vac box unit and see if that makes a difference

 

I get the feeling your trying to say that the car has had a moderate remap. A standard map would mean the car is stock.

 

Worded it a bit wrong haha, i was running a hybrid before so standard map to me would be your basic remap from stock 130 to 170-180bhp (or stage 1, as some call it)

[SuperbTWM]

'Standard remap' would have made more sense haha

 

Has the car functioned ok since having the map changed? just trying to rule out a software problem

Edited 27 September, 2016 by SuperbTWM

[Harry1212]

The car itself drives fine, even when it begins to pull at around 2k revs it pulls smoothly but at around 3k revs there's a noticeable loss of boost and then suddenly a spike and boost is suddenly back and it pulls hard, but watching the boost on the gauge is often hits 2 bar before i stop accelerating, it's sometimes ok in 3rd gear up to about 50mph but any time I do this in 4th gear or higher or under load up hill it will just go into limp mode even if the boost is at 1 bar or less on the gauge

[Harry1212]

A little something i've just found online

 

 

Four issues with P17965.
Vacuum pipes wrongly connected
Map N75 valve failed, cannot bleed vacuum to air filter
Map sensor failed, reading too high
Turbo vanes stuck in max position
A failed N75 valve should not cause over boost. It is only open to vacuum and pulling on the turbo actuator when it is energized by the signal from the ECU. If the valve fails or the ECU signal fails it will stop vacuum to the turbo actuator and "bleed vacuum" to the air filter. This stops boost and is a failsafe. Make sure the bleed pipe to the air filter is clear by pulling it off the N75 valve and blowing into it. It must NOT be blocked. If the MAP sensor and the N75 valve have been replaced then the fault is probably the turbo. The turbo vanes have been pulled open by the actuator and are sticking open causing over boost. This isn’t caused by a faulty actuator. It is usually caused by the actuator linkage being jammed. Try Clean the turbo with turbo cleaner. (This rarely works long term).Strip the turbo and clean properly. A faulty MAF should not give either under boost or over boost codes. A faulty EGR valve should not give either under boost or over boost codes, but a vacuum leak in any vacuum pipe can cause problems especially if a one way valve is not working.

[poiuytre111]

Personally I would check the MAP sensor and associated wiring, only because I had similar symptoms and found a MAP wire that had been caught in something and worn through/broken. If the MAP sensor doesn't tell the ECU about the boost being achieved, it will try to provide more up to the point it smells a rat and goes into limp mode. Having said that, your reference to boost coming and going at 3k revs is hard to explain - you sure there is no stickiness in the vanes actuator at the extremes of travel ?

[SuperbTWM]

Have to changed the map from when you had the hybrid turbo on?

[ajs_vrs]

Do a log it will give you an indication if the vacuum is knackered, mine used to make an noise when you switched it off but it was fine.