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Stock '04 STi intermittently not hitting full boost

915 views 2 replies 2 participants last post by  AdamJames 
#1 ·
I'm having a problem with my car where it will drive completely fine for awhile then only hit 8 psi. Turning the car off for a few minutes then driving again will allow it to hit full boost then after a period of time it will happen again. I've had it happen after an hour of driving and I've had it happen after 15 minutes of driving. It happens both on the stock tune and after switching to cobb ots stage 1 as well. I monitored boost and the AP and the boost gauge read the same. Monitoring target boost shows it is trying to hit 16.7. Since it resets after turning the car off and on I'm fairly certain it's not a boost leak. It also hits 8 and stays there rock solid from 3k to 7k so I feel like it's just hitting wastegate spring pressure and staying there. I did visually check all the vacuum hoses I can see and the intercooler couplings and see no trouble. The car drives perfect other than the boost issue, idle is perfect, it idles at -21 vacuum. So can my boost solenoid be flaking out? Is the sti and wrx solenoid the same?

Car is a stock 04 sti with a fresh engine and turbo. I only have 1300 miles on the new block and did a 500 mile break in so I've only been going to full boost for 800 miles.

Thanks!
 
#2 ·
This does sound like a faulty boost control solenoid but we cant rule out an air leak. Have you tried swapping out the boost controller with another one to see if your results change? I would also smoke test the engine just to be sure there are no air leaks.
 
#3 ·
I have my feelers out on a local forum to see if anyone has one I can borrow. The reason I need to know if the WRX one is the same because that would be a lot easier to find. I need to check my fiance's 08' OBXT also to see if it is the same. I know they did change it at some point.

Yeah I can't completely rule out a leak but I'm fairly confident it is not because it clears after turning the car off and back on and because when it happens it is so steady at 8 psi.
 
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