Rs2 coupe last bit of boost has disappeared

[220bhp]

The boost on my coupe no longer reaches the 1,8 bar of boost.
I have done a boost leak test, and run an expensive smoke machine through it. Absolutely no leaks.
Car runs ok but boost stops at around 1.4 bar.
The car has full rs2, with 3" exhaust, wagner intercooler, and PRJ live mapped.
Just wondering if anyone else has had a similar problem, or could shed any light on what might cause this issue.

[mike74]

Try checking the altitude sensor per this post

http://www.s2forum.com/forum/showthread.php?t=2899&page=2&highlight=F96+resistance

[220bhp]

Thanks for that. I.
I forgot to mention that the car is also using more fuel.

[Rusty]

Any codes?

[220bhp]

No codes

[simon20vq]

O2 sensor issue?

[220bhp]

I thought about the o2, but would it not show a code

[simon20vq]

I'm not 100% sure but maybe an intermittent issue? Check the connections and make sure there is nothing damaged would be my guess especially if using more fuel. Easy enough to change.

[220bhp]

The o2 sensor used on the s2 is Bosch. Has anyone used any other make without
any problems.

[hunker7]

The o2 sensor used on the s2 is Bosch. Has anyone used any other make without
any problems.

I used NGK for a while, no issues.

[Quattronaut]

With the same software, car ran perfectly befor? No changes? More fuel and less boost came up the same time? Stock wastegate spring, wastegate still sealed?

1,4 bar boost is not emergency map, that would be 0,4 bar, if WG ist stock. So it could be boost regulating, maybe N75 or it´s wiring, or the boost sensor inside ECU.
I once had the issue, that the hose before turbo choked at high boost, because it pulled together- it was the stock S2 one, without the metal ring inside of it. I changed it to the RS2 one, that has got the ring inside, and it was ok again.

Running too rich could be maf sensor or O2 sensor. I don´t know, if the iat sensor can reduce boost, when the air gets hot, or if it only cuts boost to zero, when it is too high, checkt cthat either for sure :-)

Those are the most common issues on low boost or running rich. Try to replace them with new ones, or may used ones, but fom a complete stock and perfectly running car.

[220bhp]

Haven't changed anything same map stock waste gate, and spring.
O2 changed last year, n75 not new., but checked.

[mike74]

Have you tried spraying WD40 or something similar inside the N75 to give it a clean?

[Quattronaut]

Checked N75 can be faulty, too. Checking just shows if it is dead or not. Sometimes they work weak, but still are in "normal" resistance range.

[220bhp]

Its time for a new one