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My MkV Hisses constantly under throttle with no release sound. Also lost power. I cannot find any obvious leaks.

Originally, I was Registering the CEL for MAF and P0299 (Underboost). I've replaced the MAF sensor, relieving me of the first CEL. I was hoping a DV swap would help as stated above. Upgraded to the newer rev OEM DV, but, I'm still having the same issue. I AM glad that I replaced it though because the stock unit was completely shot!

And suggestions???

...PS, really liked the timeliness and support of ECS, where I purchased the DV
 

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What mods? You out of warranty?

Most commonly it's a DV or a small boost leak, but could be these as well.
Explanation:
Faulty wastegate bypass regulator valve
Probable cause:
1. Mechanical damage at turbo
2. Faulty charge Air pressure sensor
 

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The "hissing under throttle" doesnt sound good. I would hit the dealer first if its under warranty. If not, look again for a boost leak and make sure that DV is nice and tight in there (and installed properly of course).
 

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what a coincidence... i just got the p0299 code myself. took it to the dealer and he said it could just be a sensor that sporadically registers a fault... i'm tending not to believe that, but we'll see. he also mentioned that he has replaced a sensor on the turbo itself and that is occasionally a problem that he has to work with... if it comes back up, guess it's time to have the turbo looked at, and maybe replace the dv while they're in there...
 

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what a coincidence... i just got the p0299 code myself. took it to the dealer and he said it could just be a sensor that sporadically registers a fault... i'm tending not to believe that, but we'll see. he also mentioned that he has replaced a sensor on the turbo itself and that is occasionally a problem that he has to work with... if it comes back up, guess it's time to have the turbo looked at, and maybe replace the dv while they're in there...
2. Faulty charge Air pressure sensor
 

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2. Faulty charge Air pressure sensor
exactly... he didn't have the time to get into anything today, so i'm probably gonna schedule a time where i can just drop off and come back... too much stuff that needs to be done to either attempt or wait around for..
 

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I'm getting this same code; however, I only get it when stage 1. I try to get it to come up with stock tune but I haven't had it come up. Anyway to figure out exactly why this is coming up? If it's "underboosting," is it regularly underboosting or is that faulty sensor just throwing things out there that it should be?
 

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I'm getting this same code; however, I only get it when stage 1. I try to get it to come up with stock tune but I haven't had it come up. Anyway to figure out exactly why this is coming up? If it's "underboosting," is it regularly underboosting or is that faulty sensor just throwing things out there that it should be?
You kinda need to run a log, or scan and clear and see how often the code comes back. You have a vagcom? How much is the sensor?
 

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You kinda need to run a log, or scan and clear and see how often the code comes back. You have a vagcom? How much is the sensor?
No vag unfortunately. Not sure on that sensor. My CEL only comes on randomly when I'm running the car really hard, otherwise is never comes on.
 

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i can give everyone a more accurate diagnosis after tomorrow hopefully... just took mine to the dealership to have the cel checked out finally... from what i could tell, my turbo was basically not pulling any extra power at any rpm when the problem started... the service manager agreed that it was probably the sensor... he also said he would check for boos leaks just to make sure, but he has had to replace teh sensor in a few of them before. hopefully i'll find out what exactly it was and the cost... once i do i'll be sure to post
 

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That'll be nice to hear. I've been meaning to do a boost leak test on mine--I'm just too lazy. I'm reluctant to bring mine into the shop because I'm chipped and I can't get the CEL to come on when on stock tune.
 

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Sorry to high jack, but I'm also getting the same code.

Took it to the dealer today (drove there and wasn't in limp mode, but CEL was on).

They did this:
self test on turbo systenm - no faults
pressure tested boost system - no leaks
checked DV (upgrade D version, intalled 3 mo ago) - no issues
no vacuum leaks

So, they clear the code and sent me on my way. They said the codes were due to my DP and fmic, which I'bvew run for about 4 weeks, first 2 I had no issues.

So, about 150km from the dealership I lose all boost and MIL is back on.

Seems ot be intermitent.

Figure it's the charge air pressure sensor, or the N75? - I work with sensors all the time at work and they can be tempermental, when in doubt change it out.

Any one know the part numbe, or where it is in the engine? on the ic? The dealership kind of hinted that my aftermarket parts won't let them cover it under warranty (bs but too tired to argue with VW Canada again)... so I'll have to change it myself. I hope this is the issue. I know the N75 part number.
 

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so apparently (i don't have my car back, they had to order wheel bearings for both rear wheels... yeah, that was an awful pitch of sound to try to suffer through) but they said that there was a hose loose or disconnected... i don't have a clue what they're talking about because i haven't been back since, but they said that i would have to drive it a bit, pay attention to the performance, and see if the light comes back on... if it was just a hose that slipped off somehow, sweet... i'm just doubting that it would be that simple... anyway...

as for where the sensor is, the shop manager showed me a turbo he had laying around that he ordered for some kid to part out... he pointed to a sensor on teh turbo itself and said his guess was that sensor on the top of the turbo went... i really was half awake and not paying much attention, but if i remember correctly, he said he had replaced that one on a few different cars so... maybe that's the one? i know that other people have replaced them, so i would take their word over my half awake word any day... especially since i didn't do any of this service trip on my own!
 

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I agree with the intermittent thing. Today I was not throwing a code, because I changed the file to stock tune I think, but my boost is doing some odd thing as it's kind of going up and down while WOT.
 

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I agree with the intermittent thing. Today I was not throwing a code, because I changed the file to stock tune I think, but my boost is doing some odd thing as it's kind of going up and down while WOT.
Ditto,

I rest the codes, drove fine this morning. Then this evening no MIL, but no boost and lots of surging power, had to keep it in manual otherwise it would bog down.

I'm going to focus on changing the N75 and see if that helps.
 

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so the "hose" that the dealership "reconnected" didn't do anything for me... usually these guys are great, so i won't knock them too much, but i knew something else was up... gonna take it to a dealer that's a bit closer and see if they will cover it under warranty...
 

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so the "hose" that the dealership "reconnected" didn't do anything for me... usually these guys are great, so i won't knock them too much, but i knew something else was up... gonna take it to a dealer that's a bit closer and see if they will cover it under warranty...
Any updates?
 
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