Thread: vacuum pressure

ok. i posted a thread about this before but i still cant seem to find my leak. my boost gauge reads 0 at around 1000 rpm and when it revs up to 3000 it has -20psi. i have checked all the lines and they seem to be fine. but when it is at 3000 rpms i can head a really high pitch noise and i have had my dad look while it is making the noise but no luck. so i am totally lost and i don't really have the money to bring it some where to get it fixed. it started after i put my headers in. any idea on to find it if there is a step by step or anything that would be great.

in your previous thread you said you checked for vac leaks did you check the gauge (if it is mechanical)?

Btw my gauge reads -11 at idle, am i having a problem too!!?! The car seems to run fine. Stock pulley, mods in my sig (plus a DP).

Originally Posted by TDCRacing

You will always have a vacuum at idle. Your suppose to. But not when you are at PT or WOT. Because the throttle blade is all the way open therefore there is no vacuum present in the LIM.

yea i know but i just put my headers on and now i have no vacuum i have look at all the lines. and im nit sure where to look next

People in the other thread say idle vac is supposed to be around 15-20. Mines only 11, i mean the OP's is 0 so hes in worse shape then me i guess lol.

Originally Posted by DnaProdigy

People in the other thread say idle vac is supposed to be around 15-20. Mines only 11, i mean the OP's is 0 so hes in worse shape then me i guess lol.

yea i put my headers on Tuesday and i was reading -20ish before that but once i put them on i have no vacuum

Originally Posted by TDCRacing

What is your boost gauge reading on the DIC?

have not look yet ill do that now

it reads boost at the same time my gauge does

when my car is trying to idle it wont stay running and i cant even drive it

Originally Posted by TDCRacing

What else did you tke off besides the headers? You may have a huge vacuum leak. Take some carb cleaner and spray around the LIM gaskets and all of the other areas and see if you hear the engine rev up.


That's the only thing I can think of.

just the headers thats all

If it wont stay running I say it is a vacuum leak and will have to find it somewhere. I dont think a bad gauge would effect how it runs mechanically.


FYI......on my car.....
Idle in park- -15 to -21
When in the throttle while driving 0 to +9 psi depending on RPM's and weather conditions.......
Normal driving depending on how into the throttle anywhere from -9 to +9
At a stop light while in D= -18 to -15

This is all according to the aeroforce scan gage........

Originally Posted by Liquifire

If it wont stay running I say it is a vacuum leak and will have to find it somewhere. I dont think a bad gauge would effect how it runs mechanically.


FYI......on my car.....
Idle in park- -15 to -21
When in the throttle while driving 0 to +9 psi depending on RPM's and weather conditions.......
Normal driving depending on how into the throttle anywhere from -9 to +9
At a stop light while in D= -18 to -15

This is all according to the aeroforce scan gage........

yea i disconnect the gauge and it didn't change anything

Do you have someone to help troubleshoot this. If so you said that it made a high pitch noise(assuming that this is not the SC) at 3000 rpms........open your hood and have one person rev it( short term) in this range to see if you can hear were this noise is coming from if nothing else works.........Check all fittings too. You could have a large crack in the plastic somewhere where the hose is attached if you bumped anything or pulled on an attached hose when doing the headers...... You are 100% sure that you have the EGR sealed off?

Originally Posted by Liquifire

Do you have someone to help troubleshoot this. If so you said that it made a high pitch noise(assuming that this is not the SC) at 3000 rpms........open your hood and have one person rev it( short term) in this range to see if you can hear were this noise is coming from if nothing else works.........Check all fittings too. You could have a large crack in the plastic somewhere where the hose is attached if you bumped anything or pulled on an attached hose when doing the headers...... You are 100% sure that you have the EGR sealed off?

yea it is sealed of but i had a friend listen and he thinks that where he heard it from but he was not sure

I know the brake booster line is huge and would create a large loss if disconnected....not sure what else is that large that would create a full vacuum loss.