2G: idle vacuum pressure

[foxracing4500]

mines been at -25psi is that normal? would other mods effect it like a big fmic? car idles fine btw, 1 very small leak. also my car is an auto.

[delta448]

Did you oil your air filter recently?
Maybe it's time to clean the throttle body?

That's a pretty high value. I've only seen that much vacuum when coasting downhill in gear at moderate engine speed in my manual trans cars. Just to be sure, this is with the trans in P or N and the idle below 1000 rpm, right?

BTW, vacuum is usually measured in inches of mercury (inHg), -like on a manometer.

[dsmer1]

it also varies buy altitude. how high or low are you from sealevel?

[sciondan]

Industry standard is 20in. Vac at idle on a healthy engine. All thoe DSMs usually hover around 18.

[foxracing4500]

Originally Posted by delta448

Did you oil your air filter recently?
Maybe it's time to clean the throttle body?

That's a pretty high value. I've only seen that much vacuum when coasting downhill in gear at moderate engine speed in my manual trans cars. Just to be sure, this is with the trans in P or N and the idle below 1000 rpm, right?

BTW, vacuum is usually measured in inches of mercury (inHg), -like on a manometer.

didnt oil my air filter but I will check the TB tomorrow. It is in park, tomorrow I will put it in D and N and get a reading. I only really notice it when I am letting my car warm up, its a steady needle, no bouncing. it is T'd off with my FPR if that matters.

Originally Posted by dsmer1

it also varies buy altitude. how high or low are you from sealevel?

997ft from sea level.


EDIT: checked all gears still the same in all besides reverse and drive, I have a mechanical gauge so I wanna say it read 22-23. So if 20 is healthy im sorta close but I do have emissions removed also. Once its daylight i'll try cleaning the throttle body, would seafoam effect it at all?

[NHerron]

So now it's 22-22inHg?

I would try a different gauge or check it with automotive tester like a Mityvac, just to rule out a faulty gauge.

Do you ever have problems with the tachometer dipping really low after letting off the accelerator?

[MJcanada]

mine reads -6 @ idle around 750-850rpm and -10-11psi on decel.

1inhg=0.491098psi 2.036254inhg=1psi

Ps. I'm on aftermarket cams.

[foxracing4500]

Originally Posted by NHerron

So now it's 22-22inHg?

I would try a different gauge or check it with automotive tester like a Mityvac, just to rule out a faulty gauge.

Do you ever have problems with the tachometer dipping really low after letting off the accelerator?

its shitty out but I will try my audi's boost gauge, hopefully its that.