JJO311

Last week I finally installed a VDO boost gauge in my A-pillar to be able to determine boost levels on my A4. I tapped into my vacuum line from inbetween the intake manifold & the fuel pressure regulator. All of my connections there are tight. The past 5-6 months it hasn't really had the same punch it used to when it was first chipped.

When I first installed the boost gauge, boost was terrible, like 1-5psi on hard acceleration. For some reason I had 2 holes in my front lower intercooler pipe that crosses the front end of the car. It looks like they were drilled into and spot welded (maybe from the previous owner) and these spots had started to leak.

I welded in these holes, and it no longer leaks at these locations. Now my boost is 5psi at medium throttle (~3000-3500RPM), maybe 7-9psi at hard acceleration (4000-5500RPM).

I frequently read posts on here that say a chipped A4 will hold 10psi and spike as high as 16-18psi. Im no where near this.

I checked my N75 valve yesterday with my multimeter. It reads a resistance of 32 ohms, which is on par with what I've read from on here. Can I pressure test it?

I also checked my 710N BPV. With the car turned off, no air can travel through the big inlets on the valve. I think this is correct and working properly.

I visually inspeced closely all of my rubber boost hoses and tightened all of the screw clamps holdign everythign in place. I could not find leaks.

One item I haven't checked is my wastegate actuator / wastegate. I know if its not closing all the way it will not hold boost. I read that a broken actuator will make a noticable metallic sound. There is no such sound on my car.

Are there any other things I should check to troubleshoot my boost problem? I currently do not own a VAG (maybe I can check duty cycle of the N75?).

Any troubleshooting help would be greatly appreciated!!

Car specs listed in sig...

<img src="http://pictureposter.audiworld.com/53343/jjo311_a4_sig_2.jpg">

Silver Streakin'

pressure test it. you've probably got a leak.

S4iowa

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Justin517

with the car COLD try and see if you could see the wastegate rod and reach in, or under the turbo and grab it, if it moves around freely its shot, get a new turbo.
also do a pressure test, how to do this has been covered a bunch of times, search to find out how to make and use one.
one last "thank you mr obvious" note did you ahve the car chipped? or did you buy it that way? maybe if you bought it that way...its not realy chipped?

S4iowa

He could replace the wastgate acctuator with out having to replace the turbo.

Justin517

and there were multiple cracks in the exhaust housing. The actuator is about $100, a new K03 is under $600, a K04 is $750-$850 and you get more power.
its not a bad job but you definetly dont want to do it twice if you dont have to.

S4iowa

replaceable.

Joey T

I would pull the turbo and hceck the hot side housing

Justin517

the internals of the actuator deteriorate, and the metal flapper-parts melt, if one is bad it is quite possible the other is also.
dosent have to be, but its deff possible.