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Old 09-06-2019, 08:15 AM   #1
Scooby Newbie
Member#: 506063
Join Date: Sep 2019
Default WRX Underboosting and overboosting? Timing issues?

Hey, so I bought my first WRX roughly a month ago, and have had a number of issues since then. Its an MY01 model and is completely stock engine wise.

When I first got the car, it ran on wastegate spring pressure, which took me 5 minutes to find the issue, no boost control mechanism, simply bought a restrictor pill from Subaru and went straight up to boost of around 14psi.

However, it kept dipping down to 7psi after a while of driving, so I borrowed a working BCS off a friend, as mine appeared to be sticking. This fixed my issue for a small time, and boost went slightly too high (15-16psi instead of target 13.5)

Then all of a sudden after a day or so of driving the boost will lock itself at 7psi and the car will have lots of afterfires when downshifting, possibly running a bit rich. An ECU reset fixes the issue and back up to boosting at roughly 15-16psi.

I'm not sure whats causing this small overboost, or if this tiny overboost is enough to throw the timing off on the car and cause limp mode (no CEL). Is this possibly the ECU responding to a knock and pulling timing, or is it something more serious?

I'm not certain where to go from here, any help appreciated!
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Old 09-07-2019, 01:16 PM   #2
Scooby Specialist
Member#: 29292
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Orange County CA
2004 WRX wagon


when it happens again, try disconnecting the wastegate line and see if you can get boost. if you can, it more than likely is your ebcs
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