Boost issue. Update: still have fault.. help please!

[mdss]

Hi all sorry for making my first post one asking for help but i would appreciate it if anyone can point me in the right direction.

My RS4 is not boosting properly, when you turn it on its fine for one or two quick blasts and then it goes into limp mode and hardly spools at all. I have pressure tested the audi standard dump/recirc valves and they awere fine no splits in diaphrams etc.
Then cleaned the maf and still the same the idle is perfect and no misfiring etc so i didn't think it was the maf but thought it best to clean it anyway to no avail !

Does this sound like n75 boost valve failure, i assume the car is over boosting and then ecu retarding for safety and causing limp mode??
I have heard lambda problems/maf problems.
Any help would be great is it the case that both maf and n75 need a replace or could it be something else.
Also if i can get someone with VAG.COM to check the error codes will a code pop up or is it a process of elimination.

Thanks in advance for any help

kind regards

[grizz]

You need to do a pressure test and see what fault codes it's got .

grizz

[mdss]

Ok i will do a pressure test in the morning and get it on VAG.COM and see what it says

many thanks for the reply

[mdss]

Quick Update:

It was a faulty airflow meter/maf new genuine one coming tomorrow and the fault codes as you kindly advised highlighted this so thanks, much appreciated.
regards

[mdss]

Update:
I changed the maf/airflow meter and the car the first time the car was driven it went into limp mode again, re checked the fault codes and all clear what are your thoughts on it being a dodgy n75 as after the car was switched of i then drove it and it was fine again, a little odd to say the least.

many thanks in advance for any help