Hi all, first time posting - I'm suffering with an overboosting issue on my MK1 vrs, I've replaced the N75 and tried unplugging the MAF but no improvement to my symptoms. Recently got hold of VCDS so have attempted to log requested/actual boost and put them in a graph - not sure if it actually helps other than to confirm the boost issue.
 
I plan to inspect the wastegate actuator, does anyone have any tips on how to go about this, or any other thoughts on where my issue could be coming from?
 
https://photos-2.dropbox.com/t/2/AAASOnLagrvMngEAp_C79ykmfrEBMJq2sf1KeY1spWMhiQ/12/68382102/png/32x32/1/_/1/2/boost%20graph.png/ENDrkzUY9Q8gAigC/_MqbIMhiQwbzsXUrNS2XXYmQWkyL2QW31YWI4z0iEtg?size=1024x768&size_mode=3
 
Thanks!

Sorry forgot to mention I've also checked for boost leaks and tried another recirc valve

Hi and welcome. To check the actuator you could unplug N75 and log boost (115), cracking pressure should be 5 psi iirc and should be a flat line in theory.

I couldn't open your photo? What did it show?

How long have you had the car? Is it mapped? How is the power delivery and general running? There could be other suspects but won't say too much yet, one step at a time, try that with the actuator first, it doesn't cost anything. It's possible that somebody in the past has wound on the preload, it may also be possible they've tried to cheat the ecu with an uprated MAP sensor....Anyway try actuator and let us know.

Hope that helps

mine had an overboosting issue and after changing the n75 the   problem was solved 

He reckons he's done that, was it the right one?

Thanks for the feedback, will certainly give that a go (I have actually tried that previously but didn't have VCDS at the time so no way of logging results).

 

New N75 certainly appeared to be the correct part, came from TPS and matched the current one, literally no change in behaviour as a result of this.

 

The photo is meant to show my graph of the overboosting, strange it wouldn't open, this any better? https://www.dropbox.com/s/0j3p9r071o84z90/boost%20graph.png?dl=0

 

General running of the car seems fine, it had been remapped by the previous owner (believe a generic map) and I've since had it 'RE-remapped' by a good friend that spent quite some time making improvements (very highly respected tuner). The over boosting issue was present before and after the most recent remap so I've reason to believe it's not necessarily the remap that's at fault (although I guess it could well have accentuated the issue).

Thanks for the feedback, will certainly give that a go (I have actually tried that previously but didn't have VCDS at the time so no way of logging results).

 

New N75 certainly appeared to be the correct part, came from TPS and matched the current one, literally no change in behaviour as a result of this.

 

The photo is meant to show my graph of the overboosting, strange it wouldn't open, this any better? https://www.dropbox.com/s/0j3p9r071o84z90/boost%20graph.png?dl=0

 

General running of the car seems fine, it had been remapped by the previous owner (believe a generic map) and I've since had it 'RE-remapped' by a good friend that spent quite some time making improvements (very highly respected tuner). The over boosting issue was present before and after the most recent remap so I've reason to believe it's not necessarily the remap that's at fault (although I guess it could well have accentuated the issue).

The graph is better thank you. There is a bit of a spike there when boost comes on. I think the biggest issue is perhaps that boost takes a while to come on and fluctuates a little. However a good sign is that it doesn't tail off at the top end. It's a strange one, I'm not totally sure there's much to worry about but I may be wrong. In the early phase requested and actual rarely follow each other exactly, but it is a little off. Try that actuator test and see if that throws anything unusual. It could be there's too much preload on it, although that may mean it should be above requested for longer...

Just logged boost with the N75 unplugged, it looks ok to my untrained eyes:

https://www.dropbox.com/s/vg2g9dxewnbl4pv/boost%20graph%20-%20n75%20unplugged.png?dl=0

 

I'm planning on getting a smoke test done in the new year so I guess maybe I'll just see how that goes and not worry too much.

 

Thanks again.

Just logged boost with the N75 unplugged, it looks ok to my untrained eyes:

https://www.dropbox.com/s/vg2g9dxewnbl4pv/boost%20graph%20-%20n75%20unplugged.png?dl=0

 

I'm planning on getting a smoke test done in the new year so I guess maybe I'll just see how that goes and not worry too much.

 

Thanks again.

Yeah psi wise it's spot on, but is a little fluttery so yes you're right, a smoke test would be a decent idea. If you know someone who is good with vcds (like your tuner?) he could help you log some other key blocks like fuel trim and n75 duty cycle and such, just to be ruling things out if nothing else.

Check the map sensor (remove, clean refit) ..easiest way I found was pop out the drivers headlight and you can get at it without removing the wheel, archliner, intercooler etc.

also don't overlook the pipework under the manifold and the PCV system.. mine had mostly turned crisp and ripped itself apart when I removed it.