A4 1.8T Cab Quattro - Drops Boost ??

[dares_uk]

Hi

Im starting a new thread for this now,
1 because it may get more views / answers with the right title
and 2 because its not really about a replacement turbo now.

previous thread is here.
http://www.audi-sport.net/xf/threads/a4-1-8t-quattro-cab-2005-turbo-replacement.228783/

2005 A4 Cabriolet, 1.8T Quattro.

Ive been having trouble with my car for a couple months, and has been back and forward to the garage for 3-4 weeks now for various issues, turbo, boost leak, new hose, hose blowing off, lack of power etc..
Its HAD a New Turbo, a new boost hose, and a new boost valve.
Along the way, its been pressure tested a couple times, had the timing checked, the cam timing checked etc.. both boost valves have been checked/tested.
the recirce valave has been replaced/tested. etc...
It had a new cam sensor in May/June time.


Im still having problems now though
.
Now, It drops the boost. ie in 6th gear, about 70mph 2500rpm you put your foot down and there is no boost/turbo spin, has happened in 4th too, and sometimes when booting it from 2nd > 3rd.

Yesterday was actually the worth on the way home from plymouth, 6th had no boost and changed down to 5th and 4th no boost.
pulled over and turned car off, then started and tried again and boost came back.

Yesterday it was on the Rollers for a diagnostic, below is the graph, you can clearly see the boost drops.
They suggested the recirc valve is check, the cam sensor and ecu for water ingression.

Does anyone have any suggestions on what else could be causing the issue?
maybe the N75 actuator ? MAF ?

 

[pauldazzle]

So what are diagnistics telling you? If you are getting boost back by recycling the ignition that suggests the ECU is going to limp which should trigger a code.
From your description the dreaded 17705 code comes to mind.

 

[dares_uk]

No codes are coming up.

 

[pauldazzle]

Are you using VCDS for diagnostics?

 

[dares_uk]

im not, but the garage is,
guessing the garage which done the RR used it too.

 

[dares_uk]

Well, Seems all is fixed now, ive had the car back again now for two days..
and it feels alot smoother, It feels smoother for gear changes etc..

The problem, was a sticking recirc valve.
Which the garage had previously tested apparently.

So after anearly 4 weeks in and out of the garage, and over 2 months of not driving the car much,
I now feel happy and confident with the car again.

Whilst its been in , its also had a new rocker gasket to stopa leak, a replacement oil dip stick funnel,
serviced, new oil/filters etc.. new spark plugs, new boost hose, new turbo, new boost valve, new recirc valve,
headlights alighned, a cup of water emptied out of a rear light, the timing checked, the cam timing checked,
so pretty much like a new car.