N75 valve issue

[Tatersalad]

Can anyone tell me or show me which hose goes where on the N75. I have a feeling someone messed with it and messed up the vacuum hoses position.

I also run a test using VCDS Lite and the N75 duty cycle stays at 15% no matter what revs

[Tatersalad]

I have inserted a few pictures. 1 of the VCscope mostly at idle but also revved up as you can see.

A pic of the N75 with hoses attached as follows
RED - to EGR
GREEN - to turbo
YELLOW - to the outside world
BLUE - Disappears into passenger side wing
Is this the right setup?

Next picture:
A hose with a screw in it???

Any help on all these would be much appreciated

279742797527976

[Doctle Odd]

Do you have a vacuum reservoir? Black plastic ball about the size of a cricket ball? That's maybe where the blanked hose went to

[Tatersalad]

Haven't spotted a vacuum reservoir anywhere.

[abby1]

try passenger side front wing behind wheel arch cover

[Tatersalad]

okay, but why would the other end have a screw in it?

[abby1]

to keep a vacuum check audi part num 443131541

[Martynas26]

I think egr is blanked thats is easy way disconect egr vacuum line and put the screw so u lose no vaccum and egr is not opening. Check or egr have vaccum line attached??

[Tatersalad]

EGR has the vacuum line attached.
There is good vacuum from the line that goes into the N75, there is just no vacuum from the lines that come out and run to the wastegate actuator and the EGR. The grey plug on the N75 gives 12V from the red/white wire when ignition is on.

When I put the vacuum line that goes into the N75 directly on the actuator, the lever moves up in a nice and smooth motion.
So either I have a vacuum leak somewhere ( I have tried several times to find this without success) or the N75 is faulty ( I have opened up both valves and everything inside moves freely) but seeing the other codes it could also be a short in the wiring loom or a faulty ECU.

Think I should call out an auto electrician......... :(

[Martynas26]

That car you have? And that fault codes

[Tatersalad]

1998 A6 2.5TDi Auto
6 Faults Found:
01282 - Intake Manifold Flap change-over Valve (N239)
31-00 - Open or Short to Ground
01375 - Valves for Engine Mounting; Stage 1
31-10 - Open or Short to Ground - Intermittent
01262 - Solenoid Valve for Boost Pressure Control (N75)
31-00 - Open or Short to Ground
01265 - Exhaust Gas Recirculation Valve (N18)
31-00 - Open or Short to Ground
01440 - Fuel Level Signal
30-00 - Open or Short to Plus
18259 - Powertrain Data Bus: Missing Message from ABS Controller
P1851 - 35-00 -

[Martynas26]

Yeah m8 thats sounds like a repaired car after accident.loads of shor or open to ground. Check all grounds. Its not a vaccum leak

[Tatersalad]

I've checked and cleaned the ground under the chassis member at the driver's side and the one behind the coolant expansion tank. Are there any other ground points in the engine bay?

[Martynas26]

In your car i dunno. Whats about water in ecu.? Its definitely electric problem. My guess. Trace all wires from connectors of fault codes. Or try to disconect all connectors delete faults and rescan see if anything changes

[Tatersalad]

I've checked ECU as well - dry as a bone
I will unplug and scan again in the morning.
Do you know where the N239 valve is located?

[Martynas26]

Whata valve is that?

[Martynas26]

Must be on intake manifold or next to egr. Make a picture of engine bay. Will help.

[Tatersalad]

Must be on intake manifold or next to egr. Make a picture of engine bay. Will help.

Will take a pic in morning

[Martynas26]

Yours manifold is plastic or metal? If metal so valve should be next to egr but if plastic so somewhere on manifold whats controls flaps in it.

[Tatersalad]

This is what my engine looks like. Taken from the net so ignore the red circle.
27987

[Tatersalad]

Cleared codes, unplugged the N75 and N18, read codes again and I get the exact same codes. So whether they are plugged in or not doesn't matter ...........

[Martynas26]

U got original cable or cheap ebay? u say what u check one cable and its got 12v. I know what somehow u can check ground aswell

[Martynas26]

Try another n75 or n18 from the car in which they work ok. But i think is wiring loom or ground or ecu....

[Tatersalad]

I got vcds lite with a vag kkl cable from ebay.
yeah the red/white wire from the plug of the N75 has 12V

[Tatersalad]

Update - took the ECU out and cleaned all contacts. This made a HUGE improvement. No warning codes anymore (apart from ABS databus controller error) The car runs a LOT better and no limp mode anymore after 10 minutes.

Even though there is a lot more power, the car struggles to give it's full power especially above 3000/3500 rpm.

without fault codes this might be difficult to find....

[abby1]

which ecu you cleaned where from

[Martynas26]

Glad to know you fix that electricgremlin.
Now whensensors works you can diagnose your low power. Good luck

[Tatersalad]

The ECU in the engine bay near the windscreen, under the scuttle panel in the watertight box

[Tatersalad]

Glad to know you fix that electricgremlin.
Now whensensors works you can diagnose your low power. Good luck

How do I diagnose that? Live data via vcds?

[Tatersalad]

Run test today.
MAF output was specified at around 900. The actual output never came above 650