Hi All,

I'd be really grateful if you could help me with a boost problem I am having at the moment.

Car is a 2001 Passat 130 PD, engine code AVF, kerma/alligator tune.

The car has gone into limp mode a couple of times with the error 17965 - Charge Pressure Control: Positive Deviation, graphing actual versus specified boost shows the actual is quite sluggish to follow specified particularly coming off boost. I've graphed a run this morning here:

http://www.mediafire.com/?mjrzkmri15y

It's an Excel spreadsheet, I did try to use google spreadsheets to make things easier but the graphing isn't up to much!

Yellow line is specified boost, light blue is actual boost. Duty cycle is dark purple.

Notice quite a scary boost spike at around 540 seconds!! Also whenever I come off boost/slow down or at idle specified can take a long time to get back to actual - i.e. a good example in the graph between 640 and 670 seconds!

I guess prime suspects are worn vac lines, faulty map sensor, N75 valve or stuck VNT vanes. I've replaced most of the vac lines and have a new map sensor but it hasn't made any difference. I'm not convinced about stuck VNT vanes as actuator movement is smooth over about 2 cms, and if I pull the vacuum hose whilst coming off boost the boost immediately drops.

Do you think next step is the N75 valve?

Its only recently started to do this by the way, has been fine with this tune for nearly 2 years now. I have noticed recently mpg has dropped a fair bit (I know it usually does over winter but this seems a significantly bigger drop than usual), and the turbo whistle has seemed a lot louder lately - maybe a leak somewhere but would this cause over/sluggish boost? Performance is top notch as ever, still pulls like a beast!!

Again, really grateful for any help!

Cheers,
Dave.