[SilverJester]

What should a vaccum gauge read at idle? I'm designing some evoscan gauges, and had originally set up the vac/boost gauge to read from -30 to +30. After watching the gauge I think my car might have a vaccum leak after watching the gauge. So I'm wondering what it should be reading?

 

[irmerm]

just remember that vacuum is not read in PSI, it's read in in/Hg (inches of mercury) and is normally somewhere between 17-22 in/Hg. What are you getting? Are you using the car's sensors or did you hook up an actual vacuum gauge?

 

[SiliconTek]

^ Yeah that

 

[SilverJester]

yeah I know about the in/Hg. I'm using the car's factory sensor, and logging with evoscan. I'm only getting around 8-10 in/Hg. So I guess I have a vaccum leak. Any ideas on where I should start looking?

 

[irmerm]

start by getting an actual gauge.

 

[Yxd68]

What altitude are you (actually the car)?

 

[SilverJester]

start by getting an actual gauge.

What's wrong with the factory sensor/evoscan?

What altitude are you (actually the car)?

Northern Indiana, I just googled it and I'm at about 700ft.

 

[irmerm]

What's wrong with the factory sensor/evoscan?

Without a gauge you won't know whether it's your sensor or actual low vacuum. As far as diagnosis, you listen for a Tsssssssss noise around the intake manifold while the car is running and do a real thorough inspection of all vacuum connections hooked up to the manifold. Also, the gauge will tell you if it's fluctuating at all which can help with the diagnosis

 

[irmerm]

Couple of more questions: Are you having any actual issues with unstable idle or the car nearly stalling (or actually stalling)? Those are prime indicators of a vacuum leak.

 

[SilverJester]

Couple of more questions: Are you having any actual issues with unstable idle or the car nearly stalling (or actually stalling)? Those are prime indicators of a vacuum leak.

It has been wavering a little (very minor) lately. I originally thought it was due to the fuel trims which I had scaled the maf 2 or 3 months ago for the bigger intake. I'll go outside soon and take look at this stuff soon. Thanks for the help.