Boost Issues (Still)

[Metro]

Hi everyone,

I have been having intermittent (more often than not) boost issues where the boost will drop out several times through the rev range. Since its not all the time, for example; yesterday it was fine for a good 15miles straight untill I pulled over to go in a shop, came back out, drove off and the issue came back again, I'm wondering if this issue could be electical? I have insulated all the split wires on the coil pack loom (since it fixed Rogo's problem) and that didnt fix it. Also, if it was the n75 valve, could I just unplug it and see if that makes much of a difference or would the only way to check it be to replace the n75 unit?

Took it into Audi in Derby who did the coil pack recall and they checked it over, they basically came back to me saying they wanted £130 p/h for diagnostics, but they also said it could be the turbo... which im guessing will be any dealers answer.. chuck a new unit at it and see if it fixes it?

I've replaced the old cracked plastic DV with a forge 007p, checked over the pipework for visual splits and cant find any...

Thanks a lot for your time

[beachbuggy]

Try running on just actuator pressure ie bypass the n75. You'll have less boost but it'll eliminate the n75 and you can see if there's any other issues.

[Metro]

Do I just need to get a plastic T splitter or something?

Thanks for the reply

[<tuffty/>]

No, just unplug the N75 electrically...

<tuffty/>

[Metro]

Cheers, ill give it a go tomorrow!

[Byzan Pics]

Just pull the n75 wiring plug, that will default to actuator pressure

[Metro]

So, pulled the plug on the n75 and it seems to be working fine! well, obviously down on power but fine non the least. Could this mean the n75 is foobed? any way of cleaning it or repairing it? Im going to pull it off along with the pipe work leading to the n75 and have a close inspection of it all.

Is there anything else which could be deducted from this?

[<tuffty/>]

No, doesn't point to an N75 issue... what it suggests is soft limp so the ECU is dumping boost for some reason or other... normally a boost deviation or something...

You need to get the car scanned for fault codes in the first instance and then maybe some logging in VCDS to see what s going on...

Don't take it to a dealer... they won't really have a clue and you will end up spending a fortune as they just replace part after part trying to eliminate the issue which could just be something as simple as a split vac pipe...

Take it to a specialist that has had more to do with finding these faults if you can't check the stuff for yourself...

First thing you do need to do though is find someone with VCDS local that is willing to scan your car...

<tuffty/>

[Metro]

Cheers for the advice, ill check the VCDS list.

[G60DAN]

Where do you live?

[Metro]

Im in derby most of the week and Warwickshire for the rest.

cheers

[Metro]

Is the pressure coming from the n75 to the actuator positive or negative? I'm assuming negative. The n75 to tip is loose and the pipe that Leeds to the actuator is loose on the actuator connector. My problem maybe?

[<tuffty/>]

Boost is always positive pressure, its vacuum that negative...

Loose pipes won't help but if they where that loose they would have blown off by now... its imperitive that all the pipes and hoses are where they should be and airtight as applicable else you will be chasing your tail trying to find the fault...

Like I said, scan for fault codes and go from there... check all the other pipes too...

<tuffty/>