Odd observation...

[BAC5.2]

I was driving to work this morning, and I noticed something.

My car overboosts like CRAZY. Not just normal boost-spiking (well, not normal I guess, but expected occasionally), but 11psi for the duration of a pull. Then immediately after that, I'll be running in "low" boost for a few minutes then back to stock 8.7psi. Low boost limits at 5psi and spools uber slow.

So I was curious, would a failing boost control solenoid be causing the "low" boost?

Also, if it's failing, is it possible that it's related to an internal leak? If so, then that also might account for my super low vacuum (-14 to -15inHg) and possibly my high idle (1250RPM) by causing the IAC to be overworked thus, throwing a code.

Is any of this really possible? Would it be realistic to think that a manual boost controller would solve this problem by bypassing the stock boost control?

I can understand the occasional spike to 10psi, but it overboosts to 11 and 12 on a semi-regular basis.

What do you guy's think?

[vrg3]

Well, if the ECU does go to low boost when it detects knock, it makes sense that overboost would cause it to go back to low boost for a while.

It does sound like maybe your boost control solenoid is malfunctioning. You might also want to check all your vacuum hoses and make sure they're in good shape and of the right diameter, and make sure the bleed hose has the restrictor in it.

I don't think a leak in the solenoid could account for your vacuum problem or your high idle. For one thing, you did a starting fluid check and I would expect you sprayed around the solenoid. For another, a vacuum leak generally causes a low idle in our cars. Finally, the potential leak is rather small and before the throttle body, so it's barely noticeable... I might be mistaken, but I don't want to get your hopes up.

[BAC5.2]

Will the MBC fix the boost control solenoid? Or will I just have to replace the BCS?

I did check that area, but I might have missed something, I'll try again tomorrow.

[NemesisEJ22t]

If you're having the same BCS problems I am, a MBC will fix the problem perfectly. I have noticed that my low boost mode doesn't seem to be knock related like I thought it was originally. It seems that the BCS will stick, and the only way to fix it is to go to WOT until the air pressure un-sticks the solenoid.