RE: problem with S2 92

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

Hello Stephane ... I don't know how much help I can be, but let me offer one
possible explanation based on my experience with other Audi turbos.  

Having the engine shut itself down at 4000 RPM sounds typical of an Audi
engine that is sensing a potential problem and is allowing you to use it in
"limp home" mode.  Since you only see the problem under boost my thinking is
that either the engine is producing too much boost, or the sensor in the ECU
thinks that the engine is producing too much boost.  The typical service
diagnostic is to attach a separate boost gauge to the intake manifold and
observe the boost pressure under certain load conditions.  There is a boost
curve that is expected for your car ... perhaps you can get a copy of this
graph from a dealer, or someone who happens to have the graph for the S2 ...

My two primary suspects would be the wastegate, or the pneumatic "signals"
that are sent to the wastegate.  Perhaps someone with "3B" engine experience
can correct me if I'm wrong, but it is my understanding that there is a
wastegate frequency valve on the engine, which controls the wastegate
opening from the "bottom" ... perhaps this valve is malfunctioning, or there
is a leaky vacuum hose.  

Do you know if your car still has the OEM wastegate spring installed?  If a
stiffer spring is installed without the required changes in the ECU code you
might also get into an overboost situation. 

Good luck!
Steve Buchholz
San Jose, CA (USA)

> ----------
> i've got a little pb with my car, when it's at 90°c (oil) if i push
> the accelerator hardly, at 4000 rpm, the engine shutdown suddenly, if i
> release the accelerator the engine start again. If i push the
> accelerator slowly, i can go to 6500 rpm and more than 250 KM/H. my audi
> dealer said injection and turbo were dirty and cleaned it up, it works
> fine for 3 weeks and started again, they cleaned again, said this time
> they cleaned the gas filter, works fine for 3-4 weeks and start again :(
> 
> it appear to me that there has too much compression with the turbo and
> the chip say to the engine to stop... did you hear about that before ?
>