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Old 04-24-2014, 09:41 PM   #1
Scooby Newbie
Member#: 376946
Join Date: Dec 2013
Default misfire under full boost.

2004 wrx
Stage 2.

Car was tuned prior to purchase 302hp at 20lbs. I have owned it for a few months with no problems. Recently the o2 sensor went. Changed it along with plugs and oil. Car drives like a dream unless its in full boost. Feels like a misfire, maybe fuel cut. No check engine light. If I turn boost down below 15 lbs, the car boosts fine. I'm stumped and any feedback would be greatly appreciated.

Thank you
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Old 04-25-2014, 12:03 PM   #2
Scooby Newbie
Member#: 376946
Join Date: Dec 2013

Any takers? Need help
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Old 04-30-2014, 11:48 PM   #3
Scooby Newbie
Member#: 389555
Join Date: Apr 2014
Location: Syracuse, NY
2005 WRX


sounds like fuel cut/boost cut - if thats stock turbo i would keep boost down anyways 20 lbs for the stock turbo is way to high. i would keep it at 15/16 psi max and that should stop your boost cut issue unless you get a open source tune for the 20 psi which as stated i would HIGHLY NOT recommend.
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Old 05-01-2014, 12:22 AM   #4
Scooby Newbie
Member#: 376238
Join Date: Dec 2013

could be caused to improper plug gap or heat range, could be caused by coil pack issues, could be cause by fuel pressure drop under full boost, could be ****ty fuel, could be not high enough octane fuel, could be dirty injectors. more then likely spark related or ****ty fuel related.
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Old 05-02-2014, 12:47 PM   #5
Scooby Specialist
Member#: 79934
Join Date: Jan 2005
Chapter/Region: E. Canada
Location: Kitchener, Ontario
02 WRX


I would bet it's a combination of improperly gapped plugs and coil packs that are on their way out. Or one or the other on their own.

I experienced similar symptoms. If I were to roll into boost hard, WOT, it would buck/stutter closer to 20psi. If I were to roll into boost at like 60-70% throttle, and only push 14-16psi, it would be ok.

I found out that my plugs were gapped at like 0.035" as well as my coil packs were starting to really fray at the insulation coil portion. The combination of a huge spark plug gap (spark has to travel further distance, and that extra distance requires a stronger spark to actually jump the gap) combined with dying coil packs really didn't like high boost. The spark would just arc/break up and thus creating misfires which is explained by the hesitation/bucking I experienced. A fresh set of OEM coil packs and properly regapping the plugs to 0.028" worked wonders and I could finally hold 21psi on my EVOIII-16G all day.
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