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Bad N75 or Turbo or DV?

buyingconstant7

Ready to race!
Location
Calgary, AB
Ride
2007 GTI 3 Door 6spd
Alright so I have a 2007 GTI FSI 6spd manual, picked it up about 4 months ago without about 140,000 miles on it. Already nearing 160. Was pretty much bone stock, now I'm running Unitronic Stage 1 and have a cold air intake on it to remove that stupid engine cover. Here are my symptoms:

On a relatively hard acceleration(when commanded boost needs to be over 10lbs), it picks up okay, but I feel surging, I don't have a boost gauge but I can feel the car slow down and pick up throughout the rev range in any gear, when my foot on the pedal has not moved.

I hear howling coming from my intake when it slows down so I'm guessing it's the wastegate opening(though some people say it's my intake but the surging while the noise happens doesn't make sense if that were true). It also doesn't feel as quick as it should. I had a blow off valve on it from the good old PO, removed it and found a Rev D diverter valve(from a junkyard mk5 gti albeit), and it seems to be fine. With the blow off valve on it, it had a code once for mechanical failure of diverter valve. Replaced the bov with that rev d, and no codes since.

Any ideas?
 

GIACUser

Master Wallet Mechanic
Location
SoCal
Could be worn out clutch.
Having a boost gauge would help as you could see if the increase in rpm corresponded with acceleration or not.
 

MagicMK

Ready to race!
Location
PA
Are there any CEL's? Have you scanned the car? If so, what trouble codes are coming up? Do you know whether the DV or the N75 Boost Solenoid were EVER changed? Were CELs lit up when you bought the car? Also, I know you know this, but did you check the cam follower after purchase - given that it operates the fuel pump and certainly poor fuel delivery could result in surging, and at the same time, it may not throw a CEL.

One last thing - spark - were the plugs and coils EVER changed?
 

MagicMK

Ready to race!
Location
PA
Ya know, I love how people ask questions for the forum, and then people spend time answering, and the OP never follows up. Nice.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Ride
2007 MKV GTI
Ya know, I love how people ask questions for the forum, and then people spend time answering, and the OP never follows up. Nice.
A bit similar to the FB crowd...many there are always only wanting a part suggestion given to them to replace based on their symptom description. However, and perhaps in this moment, this may not always be the case as sometimes things happen in their lives that we are unaware of.

OP, the truth is is there are almost always more than a few possible causes of a code or non-code issue. Ross-Tech's VAG-COM & VCDS or other data reading tool("data"...not just a code reader) will help when you have issues by allowing you to view real time data and function of the systems of the MK5. You will also get a bit more accurate suggestions if you list all you have replaced prior to posting. Doesn't mean one of the items you replaced was OK...I have recently looked at one's MK5 here and he had replaced his oem PCV...but it was faulty and leaking boost.
 
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MagicMK

Ready to race!
Location
PA
A bit similar to the FB crowd...many there are always only wanting a part suggestion given to them to replace based on their symptom description. However, and perhaps in this moment, this may not always be the case as sometimes things happen in their lives that we are unaware of.
I hear ya, but it's been about 2 weeks, and the OP is a new account with only 6 posts - 2 of them are in this thread. Unless you're deployed overseas or something - if you ask the question, then you should have the courtesy to follow up. If for nothing else, just provide some type of a status. Not only that, when somebody starts a "problem thread" and then follows the problem to conclusion, that becomes a useful example for other MKV owners. It's fairly frustrating when you're searching the MKV blogs and find a problem just like yours, and then there are a bunch of suggestions -- but the OP never follows up regarding the outcome.

My 2 pennies.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Ride
2007 MKV GTI
I hear ya, but it's been about 2 weeks, and the OP is a new account with only 6 posts - 2 of them are in this thread. Unless you're deployed overseas or something - if you ask the question, then you should have the courtesy to follow up. If for nothing else, just provide some type of a status. Not only that, when somebody starts a "problem thread" and then follows the problem to conclusion, that becomes a useful example for other MKV owners. It's fairly frustrating when you're searching the MKV blogs and find a problem just like yours, and then there are a bunch of suggestions -- but the OP never follows up regarding the outcome.

My 2 pennies.
...and your $0.02 is well spent. I hear you and agree...generally, it is frustrating when you give your time and one may require feedback in order to help work through an issue. When nothing is coming back from an OP, then one feels they have wasted their time. It just seems to come with the territory. Also, yes, part of my comment was meant to validate your frustrations and the other was to say each person that does this is different and I hope to give them the benefit of the doubt. Sometimes I see others have commented with no response from the OP and so I will often wait for that before posting.
 

buyingconstant7

Ready to race!
Location
Calgary, AB
Ride
2007 GTI 3 Door 6spd
My apologies all. I’m active on vortex. Not on Mk5 forums here because over a couple posts it just doesn’t seem like this is as active. Anyways, to follow up. I had replaced N75. I did plugs and coils. Replaced PCV valve, did a boost leak test(no leaks). Minor increase in drivability but it was still surging. I sourced a lightly used known good turbo for $150 and threw it in. When my old one was out I compared the two side by side. My old one had some shaft play but not much. However the main difference was the wastegate. Both actuators had no play but the diaphragm in my old turbo was definitely bad, and I’m guessing it was opening and closing when it shouldn’t have. Anyways, I put the turbo in and at the same time did my timing belt, rollers, tensioner and water pump with a metal impeller. And now, it’s great!!!! Smooth power band, much more power, and it’s so so so much fun to drive. It still has the intake howl from my CAI however I researched it’s my stock diverter valve is causing that noise and a relocation kit solves that. Either way. Thanks for your suggestions. I’ll do my best to stay more vigilant to respond to my own posts.
 
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