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All of a sudden one day my car (2004 V70R m66) started to overboost to around 26psi and from there it goes to limp mode which cuts out the boost. . No warning, no noise, no side step, nothing new happened when this started. I got the standard codes for the TCV and MAF sensor so I replaced the TCV with a genuine Volvo replacement from Fcpeuro.

It did not fix it. So I thought maybe the wastegate hose was dry rotted. I replace the wastegate hose and the hose from the pressure side of the turbo. No effect but I’m starting to really listen now and I hear what I thought at the time to be some kind of leak when it’s under boost and only gets louder as the boost increases. Just to be sure the wiring to the TVC is good I get in there and visually check and see that the 2 green (they both looked the same color?) wires are completely fine

Double check and disconnect the TVC while the engine was running and it through the code rite away so it’s good.

Now I’m thinking mechanical only problem now. I get back in there, or on there, and I get the turbo intake pipe off. I felt at the time the worm clamp was just not tight enough for my taste soooo maybe? Anyway I get the PCT out and clean it good around the grommet?/seal? And then I go to work on the tube. First gunk and soak. Then inside for hot water and dawn dish soap with a brush.

I got this bitch lookin like she’s in her birthday suit and I can’t find any cracks slits or holes anywhere I spent 30 min allows just on the belows.

Before I put it all back together I replace the hose coming from a one way valve which I also checked to make sure was working correctly. I also fitted a better hose clamp on the PCT when I reassembled everything.

Odd thing is it’s behaving a little better now but I’m still over boosting. And that sound I keep hearing isn’t exactly a leak. It’s all the boost that’s bleeding off😱

Can a bad MAF sensor cause a chronic overboost situation?
 

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I had the same thing happen a couple years ago and I can't remember what it ended up being. It was around the time I was replacing sensors like crazy. I wanna say it was either the TCV or the MAF, but it also could've been the BPS, FPS, or 02 sensor. Not much help haha but you could try cleaning the MAF, and swap some of those cheaper sensors to start.
 

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Overboost can happen only if wastegate is not opening.
You have replaced the lines to wastegate actuator which is good. You should also verify the actuator isn’t leaking itself. Apply pressure to it and see if rod moves and stays out with constant pressure.
 

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Discussion Starter · #5 ·
What exactly do you mean by “constant pressure “? I verified that the wastegate opens and closes with a small blood pressure hand pump.

Could this be a pcv issue some how?

The only codes I get are
Ecm-130a
Ecm-6805
 

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Unplug TCV but leave hoses attached and do a third gear wide open throttle pull. Should get 7-8 psi if wastegate is correctly tensioned and operating.
 

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Discussion Starter · #7 ·
I did notice that I was still getting some boost after limp mode all I caught was like 5psi but I’m trying to keep my eyes on the road.
I’m reading my boost from a boost gauge would the ecm throw a code if there was an issue with the boost pressure sensor?
 

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Did you reset ecu and get it out of limp mode and unplug the tcv connector and do a WOT to check if you get 7-8psi like contrast suggested? Did you clean the MAF yet?
 

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Discussion Starter · #10 ·
Cleaning MAF tonight.
WASTEGATE WORKS. all hoses going to the wastegate and outlet side of the turbo have been replaced.

ATTENTION ANYONE READING THIS. I DONT BELIEVE THIS TO BE A TCV ISSUE. It’s all been checked, rechecked and replaced.

Please tell me my IPD turbo back exhaust didn’t do this.
 

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No offense dude, but why are you even driving a turbocharged vehicle that makes 300hp+ with a MAF sensor code? I feel like you are wasting everyone's time, running around like a chicken with your head cut off when you have a code for one of the most important things to the engines function. Fix the MAF code first, then come back and report if it (the over boost) is still happening.
 

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Discussion Starter · #13 ·
So are all Volvo enthusiasts assholes? I didn’t have any codes until this started happening. Seriously this is the second group and here are more ppl acting like assholes. Aren’t we supposed know our cars better then most?

Do you really think I’m driving this car with the codes? I don’t have any idle issues and my mpg are fine so please u lighten me as to how it’s my MAF. Seriously I’m willing to listen hear but stop being an asshole.

This is just like trying to find my 4c fuse. On 2004 it’s not labeled anywhere on the car or in the manual.
 

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You’re ignoring all of the valid advice and doing irrelevant things. Did you do as I told you in previous post?
 

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Discussion Starter · #15 ·
Yes, can someone explain how the MAF can effect boost as in creating a chronic over boost situation? I really just want to understand the HOW, why, and when.

TCV replaced genuine Volvo part
Vacuum hoses replaced
Wastegate has been visually verified that it opens and closes.

Like I said before the car runs tip top, except for the overboost.
 

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Discussion Starter · #17 ·
If I’m missing something obvious please inform MY dumbass about it. I’ve scratching my head for over a week before I started asking on here. And I haven’t found anyone else with the same symptoms which is why I want it on the net incase anyone else has this very same issue.
 

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What was the boost with TCV unplugged during a third gear WOT pull?
 

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Was this tested after you cleared your overboost codes?

TCV unplugged and if throttle is open 100% (no fault limp mode) it should boost 7-8 psi. That is the correct wastegate preload.
 
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