No peak boost

[tstrahonja]

Car is fast, it is not in limp mode but there is no peak boost..it goes to 0.8, 0.9 bar on 3000rpm and holds almost until redline..then drops to 0.7ish on 6500 rpm..
So higher rpm boost levels seem just fine, but there is no peak boost on 3000 rpm..it used to peak boost at 1.4 bar...
So i made a pressure test...disconnected the actuator hose from n75, and blanked that hole on n75 valve..so now ECU cant control boost..so i was very careful and booted it..goes to 1.5 bar peak..probably more but i didt want to do that..
So there is no boost leak...could a broken(partly broken?) n75 cause this kind of behaviour?

 

[tstrahonja]

Tried with MAF unplugged...still the same...
Checked all vac and boost lines...seems ok..

 

[Cupra Ken]

Does the boost fluctuate slightly? it could be a dodgy n75 vaulve. i changed mine last week and mine seems to spike to1.5 bar and drop to about a bar lovely,

 

[tstrahonja]

i think i have noticed that it fluctuated a little, but just occasionally..
i am hoping to get vagcomed today....

 

[tstrahonja]

Today ive tried my friends N75..no luck

 

[tstrahonja]

Here are some logs...



Can someone interpret please?

I also got these codes...

Monday,29,March,2010,20:26:41:26365
VCDS Version: Release 805.0

Address 01: Engine
Control Module Part Number: 6K0 906 032
Component and/or Version: 1.8L R4/20VT SEA 0002
Software Coding: 11500
Work Shop Code: WSC 00000
2 Faults Found:

16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-10 - - - Intermittent
16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -

Readiness: 0010 1000


Ignore MAF fault..its there because i tried boosting with MAF disconnected...

I have a decat and used wayne angle block for o2 sensor...

16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -.....can this cause my boost problems?

 

[tstrahonja]

anyone?

 

[tstrahonja]

nobody?

 

[tstrahonja]

bump...

 

[vngtx]

is it possible the angle block is leaking?

 

[tstrahonja]

i dont think its possible, i actually checked my exhaust system...i closed it at the end, and while running on idle i was checking for leaks...there is some on connections between decat pipe and middle silencer but nothing much plus the fact that it is all after the lambda and o2 sensor...even if it was leaking...can that affect boost like this?

 

[vngtx]

i was just looking up the fault code on google and a few threads pointed to the angle block.

 

[tstrahonja]

i might try to test my exhaust again..but this time puhing a throttle a bit, creating more pressure in the exhaust...who knows..

 

[Big_daddy]

You checked the actuator hasnt loosen down?
You done a battery reset? as well as a TB alignment after that?

 

[tstrahonja]

actuator is set on 13 threads and it is stiff, i tried pulling it ..the spring is strong..
ive deleted all errors using vag-com and did TB alignment also using vag-com...the TB values go from 15% to 85% wich is ok i belive..
ive noticed something today...on idle i get 0.8bar vac..i think it was 0.7 before..
and throttle feels a bit weird..for example...when i start in 1st gear, i need to press it a bit more than before or else it will die on me....

 

[tstrahonja]

In the logs MAF seems ok because it measures over 150g/s wich is ok i belive..if there was a vac leak somwhere in the intake, MAF readings would be lower due to engine sucking some air somwhere after the MAF...am i right?
It is also noticable that ECU is requesting more boost, but turbo cant give it...pressure test?

 

[tarzan]

check all hoses for leaks pretty sure you have a leak as you don`t get the boost the car request
so a pressure test is a good idea-and check the hoses under the inlet for splitting as that can happen

 

[tstrahonja]

so i did a boost leak test and there is no any...
i also tried disconnecting n75 valve from actuator to make it boost very high..i was careful with the throttle and it boost to 1.5bar easily...so there are definitley no boost leaks..

ive checked all vac hoses..no splits
and i am still getting 1 code on vag-com

16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -

i think this is for o2 sensor..but can a knackered o2 sensor or even a knackered lamda cause very low peak boost of only 0.8, 0.9 bar?..it used to be 1.4 bar.....
and it is still holding boost very well in high revs like it used to..around 0.7bar on 6500 rpm...

any ideas guys?

 

[tarzan]

had that fault code my self but dident make any boost issue

 

[tstrahonja]

i assume that this faultcode is there because the boost isnt high enogh on mid RPM therefore car is overfueling...
everything points to N75 opening wastegate too early..i might try another N75 -.-