Turbo cutting out
Hi, I've just joined the forum but noticed your problem exactly matched my own a while back. After scouring the forum for ideas with nothing tried resolving the problem, I finally (reluctantly) resorted to asking my local Audi/VW specialist garage (not a Audi dealer note!) to take a look. They had the vehicle for several days and tried ALL of the valves/pipes and usual things that cause similar problems to no avail.
Basically the ECU was seeing an overboost condition every time I started the car and accelerated. The ECU then went into a 'safe' mode which prevents any boost by bypassing the turbo (holds the wastegate wide open I believe) and the car was sluggish and maxxed at 50mph. No indication is given that this has happened as the ECU doesn't appear that clever at showing an ECU fault light. Stopping the car and restarting reset the ECU every time but the problem immediately reappeared next time it boosted.
Finally they removed the turbo and found that the wastegate was sticking slightly. They dismantled the wastegate flap (crude device...), quickly polished the wastegate shaft to remove corrosion and refitted it, all within 90 mins eventually. The car's even better than before now and no problems in 18months. Incidentally the car had done 53,000 miles only. I was charged a whopping £105 all in for 3 days tinkering! Hope that helps (if you can find a similarly experienced, honest and trustworthy garage (or do it yourself).
