ta ace

iTrader: (22)

started the car to start tuning noticed that when i push the brakes the pedal falls and feels squishy (like the brakes need bled) and the idle jumps up to 2000 rpms and the vac raises a little bit.

my question is i see no gasket between the booster and master cyl. nor do i in any parts diagrams maybe the booster has developed a leak on the inside cabin side? i dont believe our cars have a check valve in the hose from booster to intake do they?

any ideas boost leak test shows no leaks.

barneyb

There is a check valve but the check is in the direction of air moving to the booster.

ta ace

iTrader: (22)

ill check the valve functionality on my lunch break

so it allows air from booster to intake but not from intake to booster

MechTech

It allows vac to go from the intake to the booster but does not allow anything back to the intake from the booster

ta ace

iTrader: (22)

checked on lunch it seems to be working

i disconnected it from the booster
i could blow through that end but i would not suck through that end (towards the booster)

SStoEVO764

sounds like the diaphram inside the brake booster is leaking vacuum. pinch the hose off so nothing can get through it and check again by pressing the brake pedal to see if your idle rpm changes. You can also check by your fuel trims while pressing the pedal and off the pedal.

ta ace

iTrader: (22)

ill check i hope its not the cams not creating enough vacuum to supply it

ta ace

iTrader: (22)

everything looks good and working but maybe the cams just make lower vac and when the brake is pressed it allows press into intake making the idle raise a lil?

MechTech

Try capping off the booster line @ the booster and press the brake and see if the idle still changes. Obviously dont drive the car this way.

ta ace

iTrader: (22)

did this and no when its clamped it doesnt happen

i think what is happeneing is the cams are so large they are not making addiquit vacuum so when i push the brakes it needs more vacuum as i push them... making the engine rev up to create the needed vacuum to supply the brakes

MechTech

Possible but id say unlikely. There is no parameter for engine vac to increase idle speed. And once the vac "caught up" with the need for more vac the idle should come down. Do you have a vac/boost gauge? Wat are your readings?

MechTech

Also it shouldn't need to go all the way up to 2k to create significant vac