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Discussion Starter · #1 · (Edited)
Hello! I have a 2006 S60 T5 (I'm not sure what turbo people think is in my car, the IPD guy told me a TD05, but after pulling the thing the other day I'm 99% sure it's a K24). It's got a newish engine (around 110000 on the motor) and 195000 on the car and turbo. Manual tranny.

Around 6 months ago I got the stage 1 tune from Hilton, everything else stock (before you get any ideas, reverting to the stock tune changes nothing at all, just lowers the max boost when issues start popping up). Worked great, but would occasionally stutter at full boost (I have a boost gauge), like fluctuating between 15 and 18 psi multiple times per second, and shudder the car with the power fluctuation. This would only happen maybe once a month, and I just thought it was weird but didn't think anything of it. Then one day it started doing it all the time, like whenever I hit full boost. I thought it was the TCV, so I replaced that, but it didn't do anything. So I asked on here and was told to get a CBV replacement spring and diaphragm from IPD because the rubber was probably ripped and not holding pressure. The shop tried installing it with the turbo in the car, but was unable.

After they tried, and said they could only loosen one bolt, it started making what sounded like a hissing sound that changed pitch with the rotational speed of the turbine (sounded like the turbo on a big turbo-diesel truck), and would fluctuate between literally being unable to boost over 0 psi (except between 3 and 4 thousand rpm, when it would boost quickly like normal and hit max boost before dropping immediately back down to 0) and boosting like normal, but with no max limit. It would fluctuate to the opposite option once every few days. Thinking they must have left a boost leak with not tightening the bolt on the CBV housing enough, I dropped the turbo and went to replace the diaphragm myself.

The internals of the CBV looked almost brand new, the rubber was flexible and no cracks were seen. I tightened the thing down like mad, and reassembled the turbo (the parts the people on here and at IPD insisted would fit did not, but it looked good so whatever). Same hissing sound, but it was then pointed out to me that it matched the turbine speed, not the actual boost, so probably wasn't a leak. I'm not really worried about the sound, but it's back to not making more than 0 psi at full throttle again, just like before.

It threw 4 codes a couple days ago: the first two were just related to boost pressure not being what was expected (duh), but the second two were "Oxygen sensor signal faulty" and "oxygen sensor signal too low". I have also found that resetting the ECU will always allow it to boost like normal again temporarily, but without a max boost limit of any kind. It just hits max boost then stutters rapidly as it continues boosting to infinity. The ECU reset fixing the lack of boost and O2 sensor codes make me think it is a bad O2 sensor (it also has trouble starting occasionally and infrequently has a rough idle).

I have the IPD HD TCV and unplugged it to make sure it didn't fail, but it didn't change anything, which instead makes me think it's a bad wastegate actuator.

Oh and the hoses all look good and sealed, can't hear any leaks with them.

TLDR: There's a hissing sound like you can hear the turbine, boost has no max but stutters rapidly at anything past full boost, boost sometimes goes away and cant get above 0psi, CBV is fine, TCV is new, hoses look fine, an ECU reset fixes the no boost problem temporarily, unplugging the TCV only made boost spool slower, and the O2 sensor threw faulty codes.

I'm not sure what the issue is, but I just wanted to see if anyone on here has any suggestions before I drop a bunch of money trying to buy both new things.

Also, I may make a new thread for this question, but is there anywhere that sells a new wastegate assembly for less than $200?

Thanks!
 

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Replace the O2 sensor first and foremost if you're getting codes for that. That probably won't fix your boost issue, but your car should at the least run better. If you can, I'd highly suggest getting your car VIDA scanned for further codes or faults unless that's how you've already scanned it. It'll tell you so much more than a normal code scanner will though. You could replace the wastegate, and there's ways I believe to test if it's holding at boost pressures. With your tune, a new one may not be a bad idea anyways as there's ones you can get with a stiffer spring inside to handle higher boost loads that a tune will produce. I'm sure you have already, but double check all hoses, including the intake and intercooler hoses. I had my chargepipe pop out of the intercooler hose and it was throwing a code and even stalled at idle before I discovered the issue. Everything was perfect after getting that all tightened back up. Also the EVAP hoses around and under the intake manifold are very prone to cracking and splitting. Maker sure that hasn't happened either as it'll affect things. Check what you can fit before thing down for a new turbo that may not even be the problem in the first place. Good luck.

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Discussion Starter · #3 ·
Thanks! Yeah, I did a VIDA scan and those were the only things that came up. I have also had a cracked intercooler pipe, so I checked those for sure, but I didn't know about the EVAP hoses, I'll check those today for sure.
 
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