Boost Solenoid

[humeysd40]

He guys, replace my BCS with a genuine boost solenoid grom nissan.
Before i was getting 18-20psi anytime.

now it goes up yo 20 then drops, sometimes doesn’t even boost. My gauge playing up or the BCS? I connected vacuum lines correctly??

 

[BarneyB]

That doesn't seem right, but I'm not sure it's broken.
My YD25 D40 does a similar thing, where it pulls the boost down a little after the initial surge, but it's more subtle than what you're seeing.
Are all your vacuum lines in good condition?

 

[humeysd40]

Yeah theyve all been replaced

 

[BarneyB]

Maybe the actuator is dying?
If the diaphragm is only half buggered it might hold vacuum initially & then bleed out quickly?
(I'm assuming the VNT failsafe logic is designed to open the vanes...?
i.e. fail = no boost)

 

[BarneyB]

Might be worth clearing any stored ECU codes too. Maybe the old BCS triggered something when it was buggered?

 

[humeysd40]

Yeah but boost seems to have been okay on my psi gauge until i replaced the hoses and bsc weird maybe the vacuum lines are a different diameter, i replayed them with 3mm hose but looked thicker than ones before