Okay, so I know its a poor man's GTI, but I have an '08 GT Sport with the TSI 170 engine which has I've had nothing but issues with since I've owned it. I absolutely love it when its running properly, but those occasions have become few and far between recently and my local dealer and independent seem are at a loss with how to fix it.
The problem...
When accelerating the turbocharger fails to engage at the Supercharger/Turbocharger switchover point (about 3200rpm). The boost gauge shows full boost from the supercharger until this point, then drops to about a quarter when the turbo kicks in and will not move. When the car is running properly you are barely aware of the changeover, and the boost gauge will continue to show full boost as long as my right foot is on the floor.
Attempted solutions...
My car has now been in the workshop 3 times while a main dealer and an independent have tried to diagnose what is wrong. The car is on its 2nd turbo already (had a new one fitted under warranty about 18months ago) and the N75 valve has been replaced too. There have been no fault codes logged on the ECU.
Recently, the engine began idling eratically and stalling randomly. This did log an error, and my dealer got excited as he thought the problem could now be fixed. I was convinced it was a separate problem and, after having a new engine speed sensor fitted, I was proved correct. The idling/stalling problem has been fixed, but the issue with the turbocharger remains. Annoyingly, it is intermittent (though increasingly frequent), and when I took a VW Master Technician out for a test drive the problem did not rear its ugly head. Sod's Law, it did on the drive home.
Your suggestions...
Before I take the car in for a fourth time, I am looking for any help/suggestions you may be able to give as to what to look for? Anything at all will be much appreciated!
Cheers!
PS - I should point out that I am not a boy racer who drives everywhere with my right foot glued to the floor, but when I do accelerate to overtake for example, the loss of boost can, and has, created some hairy situations.
