Hi.

When i turn on the egnition on my S4 with S5 turbo engine, i hear a ticking sound from the turbo boost pressure control valve, located on the oil filler neck. When i put my finger on it, i can feal it ticking, and i also hear the ticking.

The the valve abut to die?

 

That would be the turbo duty solenoid, which is only used under boost. Under other conditions, I believe the ECU will not leave it energized. If it's clicking, that would suggest the ECU is switching it on and off repeatedly. How does the car boost? Is is making ~7.5psi, or only ~5.5psi w/out a boost controller?

 

I dont konw how the car boosts on full throttle, since i havent pushed it so hard yet, i need to do some service on it before. But reving it in neutral above 5000rpm, the turbo starts boosting.

 

That doesn't really tell you anything though. You can try pulling the plug on the solenoid, and then use a multimeter to see if it's getting a 12V signal over and over again.