Intake Manifold Vacuum Pressure

[1 fast eclipse]

Hey guys what's up my car is acting really weird the vacuum pressure is sometimes at 18 inHg but then sometimes it's at 15 inHg. I noticed that it's at 18 when I ride the car in the morning when it's kind of warm then 15 at night when it's cold it's really weird it's suppose to just stay at 18. Can someone help me pleaseeeeeeeee.

Thanks,
Leo

 

[CraigB]

Ok is this a reading from the cars map sensor or a boost gauge?
Is this at idle or cruising speeds?

 

[DSMeclipse4G63]

ok here I go.... if the cars is at idle then dont worry 15-20 vac is fine. With load its a different story. as long as this is at idle your fine, weather will affect just about everything in a car.

 

[pneumo]

When the lights are on the idle speed controller opens up a bit to keep the idle at 750 rpm. That will reduce the vacuum.

 

[1 fast eclipse]

Ok thanks guys this helps me a lot now i don't have to worry about this problem. And oh yeah i'm reading this off an aftermarket boost gauge.

Thanks,
Leo