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Discussion Starter · #1 · (Edited)
So I recently bought a Subaru and it has a few things done to it and I need some help because I am going out of my mind.
I'll list some modifications and some other notes and things that I've tested.

Modifications/Specs:
-90,000 Original miles 02/19/18
-Cobb v2 Access port
-Invidia N1 Catback
-Downpipe
-Turbo XS BOV
-Perrin Cold air
-Perrin top mount intercooler
-Stage 2 clutch

Unknown Issues:
-Choking/hesitation at 4,200 RPM to 5,000 RPM with WOT (Jerking almost) :schwing:
-Can exceed this range with little to no throttle engaged (builds up)

Notes/Testing:
-boost shows no hesitation
-Tested and cleaned air filter and MAF sensor, after cleaning it was almost worse with the (jerking)
-Cobb tuning software shows throttle position sensor. (Idle 5%) Normal numbers when pushing throttle down in neutral until 50% (Actual pedal distance) then jumps from (50%-60%) straight to (100%) after pressing further (Actual pedal distance 75%-80%) Can push to floor without numbers changing.
-Good mpg with regular driving.

Other:
Car just jerks when you WOT at the 4,200 mark. I can post a video link (link below) if needed to show some visual presentation.
I tried to link up the cobb tuner to the computer but was unlucky with the Accessport manager.
I just bought this car 2 days ago from a private party and I am new to the Subaru gang but I know my cars and when somethings acting funny I do everything I can.
This is my first post in a forum ever, sorry if it's any bit sloppy.

For the visuals: Youtube link: https://www.youtube.com/watch?v=Z10_dJWSIdU
 

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Sounds like you are getting a misfire. Unless you have a custom tune for that intake it would be my first suspect along with some sort of boost or intake leak past maf like the turbo inlet.
 

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Looks like a misfire to me. I'd stop driving it and take it and get it looked at, or if you are capable do a vacuum and boost leak test. Check the plugs, and coil packs. I would also contact the previous owner and ask who did the tune for him. They may take a look at some data logs at no charge or a greatly discounted rate.

Also remove the bov, it's not doing you any favors in this situation and may be a source of leaking. Find the factory bypass valve, or set that to full recirculating
 

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Discussion Starter · #5 ·
Took it to my local dealer and they spent probably 8 hours looking at it, they claim its the boost sensor solenoid. It's getting too much boost under load and the more you get on it the more compression and its starving the engine from gas and getting too lean. Everything else under the hood looks perfect. They returned it to stock tune before testing and was same result. They are gonna replace the solenoid but if the problem persists they will have to look further.
 

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Personally I doubt they had all the stock equipment sitting around their shop to install and test on your car. I had to order parts much more prone to failure like could packs and sensors.

The equipment you have listed my guess is misfire from overboost. Something that is a limitation of the stock wastegate. It's even worse when it's a catless downpipe. Add an intake and it get even worse. It could be the solenoid, but I would get a second opinion from a shop that knows modified Subarus.

May I ask how you know the tune is correct?
 

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Discussion Starter · #8 ·
To my knowledge it's never been pro tuned, but the accessport shows the appropriate tune for mods listed like Aftermarket intake, exhaust with 91 octane, etc. There's a guy I spoke to on the phone that could pro tune it for me if it's not the solenoid sensor. I would have to drive to his shop and he could figure out the problem a long with a dyno tune.
 

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Your tune is 100% wrong. Cobb doesn't support any intake besides theirs and I believe aem. I'm convinced the tune is the culprit. Coupled with a fuel system at it's absolute Max or beyond with your mods.

Doing any further work without addressing the tune on the ecu is completely futile. At this point you need a etune or Dyno tune, put on a factory bypass valve, and upgrade your fuel pump and injectors.

I just want to clarify where your issues are.

First, the stock wastegate is prone to overboost and boost creep with an aftermarket downpipe. The only true solution I know of is an external wastegate.

Second, all intakes are not equal. A generic tune does not work across the board for them. Cobb specifically lists the intakes their tunes work with. Perrin is not one of them. It requires a custom calibration.

Your fuel system, with just an exhaust and intake, is at it's limit. Where you are you really need to be considering fuel modifications to address it or you are limiting yourself and risking/adding to your misfire problem.
 

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Parts that are installed that the Cobb stage 2 OTS map supports:
-Cobb v2 Access port
-Invidia N1 Catback
-Downpipe

Parts that are installed that are NOT supported by Cobb OTS Stage 2 ECU calibration:
-Turbo XS BOV
-Perrin Cold air
-Perrin top mount intercooler


You should consider removing the culprit parts or having a custom ECU calibration performed.
 
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