Asz overboost problem

[leerobson]

Hi guys, I'm new to the forum and thought I'd ask for some information about this all too familiar overboost problem on TDi's:1zhelp:

I have a 2002 130 PD ASZ golf which seems to keep overboosting and losing power when pulling hard uphills etc.

I've done all the usuall things - Had the turbo off and freed everything up( vanes, actuator etc), cleaned and made sure EGR was all free, checked all the pipes to the valves( N75 etc), tested resistances of the sesnors, swapped Maf and Map sensors from a car that worked perfect, tested wiring between ecu and sensors, tested with Vag-com on measuring blocks 11 which seems to show a high duty cycle -

At 2982RPM - 1662REQ BOOST - 2187ACT BOOST - 94.0DUTY CYCLE
3024RPM - 1662REQ BOOST - 2211ACT BOOST - 94.4DUTY CYCLE
3108RPM - 2346REQ BOOST - 2281ACT BOOST - 80.9DUTY CYCLE
3192RPM - 2346REQ BOOST - 2983ACT BOOST - 94.4DUTY CYCLE

I've also had a vacuum gauge in line with the turbo actuator(N75 pipe) and at full throttle it registered 0 vacuum(full boost) but never regulated it back to lower the boost (I tried it on the car that I tried the MAF sensors etc from and it regulated back to about 20 Kp at full Load).
I'm thinking it may be the ECU but as thats fairly expensive and not something you can swap from vehicle to vehicle to try I was wondering if anyone here would have any ideas?
Many thanks and sorry for the long post but I thought it would help explain what had been tried, I'm getting fairly frustrated with it now as you might expect:D

[kenney]

Hi Although you might get the right resistance,try replacing N75

[leerobson]

Hi kenny, thanks for the reply.
Sorry I forgot to say that I tried swapping the N75 and EGR solenoid valves round but found the car acted exactly the same, although I'm not sure if they are exactly the same valves?

[kenney]

Hi They are not the same!

[leerobson]

hi there,
just tried changing the N75 valve today on the car but found still acting the same i'm afraid.:( Not quite sure what to try next, does anyone know where i could maybe send the ECU for testing? Or would it be an idea to try and get a software update done at a VW garage. Being up here in Orkney the closest VW dealer is in Inverness 100 miles and a boat trip away. Any Ideas? Thanks

[kenney]

Hi i take it you have an overboost fault code logged on the ECU? did you clear the code before you replaced the N75 valve.I see from value block 11 it is when the revs are at 3192rpm you are getting the over boost i.e 2983. Were the parts you tested from the same type of engine?.It is very seldom there is any thing wrong with the ECU. although you could remove the contact i have seen corroded pins on a couple of cars.Clutching at straws,but how ever try all 3 components at the same time Last straw,loosen the front exhaust pipe from the manifold,you do not have to remove it,just loosen it enough that you can get something between the joint so there is free exhaust.

[Nutty]

sounds like the same symptoms as this thread

http://www.vwaudiforum.co.uk/forum/showthread.php?t=22899

[FLENG2008]

i have the same problem, there are loads of theory's
maf sencor
blocked cat
turbo vanes
vacuum pipes and more
i dint even know there was a map sencor in the intercooler?? :confused:

im gonna take my turbo and inlet manifold off when i get time and get crasher to clean it and hopefully that should sort me out, if not i give up

surely all these problems cant be diff. on the same car? can it? hasn't anyone pin pointed this common fault yet? :zx11:

[Nutty]

The MAP sensor would be an easier job to change than the turbo etc, and as the Turbo had already been cleaned (in this instance) I had assumed the turbo had been eliminated, the MAP should be located on the intercooler..

Edit

What is a MAP sensor anyway ?

http://www.madabout-kitcars.com/kitcar/kb.php?aid=213