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Hi DMV, your boost/fuel problems seem familiar. My first recommendation is read as much technical stuff as you can about the EJ25 (I read everything technical on nasioc).
Seems like there may be several things happening at once and that makes troubleshooting difficult.

First, how many miles does your car have? A well known problem is the OEM turbo inlet tearing around 100k (mine tore around 120k) and then the car runs lean and boost is all over the place once you pass 0 psi . The problem is you usually can't see the tear. It only becomes visible when you remove the turbo inlet.

Second, have you checked the spark plugs AND are they the correct ones? When I bought my 2006 WRX the last service shop changed the plugs but used the Impreza plug instead of the WRX plug. The difference is significant. The gaps are around 0.040" and 0.025" (don't quote me), but the point is I had several misfires when I went into boost and/or at high RPM.

Third, are you certain you are running an official COBB map? Download the manual and read it. Then restore the official COBB maps on the accessport and choose the one that best matches your setup (probably stage 1 91 oct).

Fourth, do you have enough fuel? Is the fuel pump due for a change/upgrade and has the filter been replaced? If you're planning on keeping the car a while, I would recommend a 255+ lph pump and a steel mesh filter.


Last but not least, I am in Pittsburgh, PA and started an engine building shop last winter.

Good luck with your diagnostics.

Tony
 

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Discussion Starter · #24 ·
Hi DMV, your boost/fuel problems seem familiar. My first recommendation is read as much technical stuff as you can about the EJ25 (I read everything technical on nasioc).
Seems like there may be several things happening at once and that makes troubleshooting difficult.

First, how many miles does your car have? A well known problem is the OEM turbo inlet tearing around 100k (mine tore around 120k) and then the car runs lean and boost is all over the place once you pass 0 psi . The problem is you usually can't see the tear. It only becomes visible when you remove the turbo inlet.

Second, have you checked the spark plugs AND are they the correct ones? When I bought my 2006 WRX the last service shop changed the plugs but used the Impreza plug instead of the WRX plug. The difference is significant. The gaps are around 0.040" and 0.025" (don't quote me), but the point is I had several misfires when I went into boost and/or at high RPM.

Third, are you certain you are running an official COBB map? Download the manual and read it. Then restore the official COBB maps on the accessport and choose the one that best matches your setup (probably stage 1 91 oct).

Fourth, do you have enough fuel? Is the fuel pump due for a change/upgrade and has the filter been replaced? If you're planning on keeping the car a while, I would recommend a 255+ lph pump and a steel mesh filter.


Last but not least, I am in Pittsburgh, PA and started an engine building shop last winter.

Good luck with your diagnostics.

Tony
Thank you for your feedback, I'll start looking into the technical stuff behind the EJ25.

First, my car has a little over 150k miles so I'll definitely do some research on the turbo inlet. The boost isn't all over the place, it just seems like it's consistently limited. I floored it on the highway yesterday and it held a consistent 7.14lbs of boost.

Second, I have not checked the spark plugs, at the time of me posting the initial post I had only had the car for a few days. Shortly after, the turbo feed line sprung a leak and I had to wait a week for the part to come in, so I haven't been able to spend a lot of time with the car since I've had it. I'll check them at some point, but I'm not noticing any misfires and the misfire codes haven't came up more than once since I've had the car. It does pop if I let off the gas suddenly after letting it build boost in 1st-3rd, but between the blow off valve and exhaust, I think that might be normal. I know for a fact that my exhaust doesn't have cats.

Third, I am 90% sure that I'm running an official map. I restored the "off the shelf tunes" and went through all of them to see which ones would work. The only one that doesn't give me boost problems is the Stage 1 Economy Mode v400 tune.

Fourth, I do suspect fuel problems. I have no clue if the pump has been changed or if the filter has been replaced at all over the 150k miles this car has on it. When I look at the fuel pump load gauge, it hit's 100% at 30% throttle.

Thank you for the luck and feedback, I want to take this car through all 50 states at some point, so I might fly through Pittsburgh PA in the future.
 

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Discussion Starter · #25 ·
Update:
I decided that it was most likely a vacuum leak, so me and a friend took apart the intake all the way down to the turbo and put it back together. We found several loose hose clamps, upon putting everything back together nice and tight, the car runs better than ever! However now I'm hitting upwards of 20lbs of boost and will even get a "boost limit exceeded" code if I push it hard in 5th
 

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Discussion Starter · #26 ·
Update:
I decided that it was most likely a vacuum leak, so me and a friend took apart the intake all the way down to the turbo and put it back together. We found several loose hose clamps, upon putting everything back together nice and tight, the car runs better than ever! However now I'm hitting upwards of 20lbs of boost and will even get a "boost limit exceeded" code if I push it hard in 5th
Finally running sub 5s 0-60 and 13s in the quarter mile!
 
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