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Sti boost loss

1064 Views 9 Replies 5 Participants Last post by  NWSTI
2010 STI hatch 6 speed. 2.5T, catback exhaust, CAI. 91K miles.
My issue is boost loss. So here’s what it does followed up with what I’ve already tried.
It sometimes does it while im driving, in between shifts or I’ll have boost, turn the car off, go drive again later and it’s gone. But it cuts boost down to 1psi in sport mode and 3psi in sport sharp when it does this. Any gear, any rpm it limits it to those numbers depending on what driving mode I’m in.
I have a cat back exhaust, cold air intake, and I’ve noticed the previous owner had removed the purge valve for the evap system although I have not once gotten an evap related code. The only Code I do have that comes on and off randomly is a park/neutral switch code that I haven’t gotten around to fixing due to it being such a pain in the ass on the manuals (on top of the tranny.)
maybe when there is a fault code it automatically cuts boost as a fail safe?
I’ve replaced the EBCS, plugs and coils, and replaced any ripped or damaged turbo/intercooler/throttle body couplers. I have also done a throttle relearn which fixed the issue for about a week then lost boost again. To make it all the more confusing to me, regardless of if the check engine light is on or not, if I disconnect the battery and reconnect I will have boost for a little while, but it will go away. Also, if use my scanner and clear the codes, regardless or if there is any active codes or not, I will have boost for a little while. I’m stumped on where to look next besides a smoke test, but I don’t believe I have a boost leak due to the fact that electronic procedures will temporarily fix the issue but maybe I’m wrong.
Smoke test, injector drop test, and turbo inspection are up next. Let me know if there is any test I should do or if anyone has had similar issues. Thanks
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First off, you're asking for trouble if it has an intake and its not tuned, I would figure that one out first. Do you have any data logging ability?
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