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Old 11-25-2019, 08:31 PM   #1
Scooby Newbie
Member#: 487192
Join Date: Jun 2018
Location: Savannah, GA
2004 WRX STI

Default Smooth Idle, Dies Beyond 20 Percent Throttle Opening

Evening Everybody,

I have an issue I've been chasing for some time now and it seems I am having trouble getting this figured out.


- 2004 STI

- Stock EJ257

- Arashi 20G 3in 10cm Internally Gated 15psi

- MAC 3-port EBCS

- Catless downpipe

- 3in Inlet

- Stock Yellow Side Feed Injectors 550cc

- 340lph Fuel Pump

- Short Ram CAI

- Cat-Back Borla Silencer Exhaust


- Stock BPV

- NGK One Step Colder plugs


- Currently in the middle of E-tuning my car through OpenSource, RomRaider/ECUFlash.


Car wants to take time to start, then wants to idle just fine. High idle during warm up process, then 900rpm idle when warm. Once given throttle, anything beyond 20% throttle as I'm watching the Logger, the car wants to almost choke itself. If you have anything less than 20% throttle it wil slowly climb in RPMs. But, once it reaches 2500-3000RPMs the car wants to stumble and fall on its face.


While driving the car, it will drive just fine for about 5-10 minutes, it is not consistent, and then it will not go beyond 2500-3000 RPMs. Same issue with the throttle as it will not let me reach beyond 20% throttle opening without having it fall on its face. It will then drop very low in idle and work its way back up to about 1200RPMs and then smooth out and drop back down to 900RPMs. This entire time, when in vacuum, the boost gauge reads -20.


- The tuner has since mentioned checking all of my grounds and then trying it again. I have checked them all, cleaned them, and tightened them down.

- I have cleaned and resealed the MAF sensor with a new O-Ring as this what brought up in other forums.

- I have gone through all of the FMIC piping and taken it apart and resealed it as a vacuum/boost leak might be evident.

I can supply data logs if anyone is interested in looking over them.

Thank you,


Last edited by That_04_STi; 11-27-2019 at 05:33 PM.
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