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VW MKV-A5 Golf/Jettas Discussions area for A5/MkV Jetta/Golf (2005/2006 PD and 2009 CR).

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Old September 20th, 2011, 22:23   #1
Join Date: Jun 2008
Location: Atlantic Canada
TDI(s): 2010 GTI DSG
Fuel Economy: 40+
Default Turbo Underboost

Hi all,

Been a long time since I've been on these forums. I used to run MK4 TDis but in the last year i've come into a MK5 (2006) which was working fantastic until recently...

Quick story. The car came from a one-owner, lady driven, always dealer-serviced and properly maintained owner. It had 227xxx kms on it when i got ahold of it. A few months after buying it, the transmission mounts broke and the motor dropped on the driver side. It was never the same.

Now, with a CEL code that reads turbo underboost, I've been struggling to get it back to normal. Here's the situation, normally the turbo would spool around 2000 RPM with a distinct whistle and noticeable pull. Now, the turbo doesn't spool until about 2500-2600, there is a minor whistle, and it seems verrrry lazy. Also, when driving on the highway at about 65MPH, if I come to a hill and need to give it about 1/2-3/4 throttle to maintain my speed, sometimes I will get limp mode. Now, when I shut the car off and restart it, limp mode is gone and I'm back to ^. This is extremely frustrating.

I am almost positive there are no obvious leaks anywhere in the turbo system. I have replaced the fuel filter, and after doing that the CEL went out, but symptoms still present (although limp mode is more rare now, but still present sometimes). A friend suggested replacing the N75 solenoid up near the firewall on the driver side (correct me if this is not the N75 or maybe that's not what it's called altogether). I haven't done this yet.

Will I be stuck with this new turbo 'attitude' (later spooling, lazy, and quiet whistle) or does anyone think it is possible that something is still wrong?

Any input at all is greatly appreciated!

Thanks for reading,

- Allan
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Old September 21st, 2011, 00:58   #2
Join Date: Sep 2005
Location: Spicewood, Tx.
Fuel Economy: 49.3, 48, 21.2,19.99

Advice..take a very good look at the EGR cooler...If its OK, then the ASV/EGR valve warants a look.
2018 F150 3.5 ECO 3.55 10spd 20s 2tone 26mpg 2turb
2006.5 DE DSG, RC2, Sunroof, 200K miles, 61MPG best
2005.5 Jetta-5 SP LSD Spec S2 130K ELF506 10-30W OCI=20k ORIGINAL CAM RSB Diesel custom 2.5DP/3" SS Pkg 1 Auto-dim mirror auto-WW auto-climate 248tq=150HP RC2 lowered 312 brakes
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