what should the vacuum pressure be in a stock 91 mustang gt and could someone explain vacuum i dont know how it works when i am in 5th gear it goes down to 0psi when hitting the gas in 4th gear when hitting the gas it goes to 3psi in 2nd gear it goes to 5psi and in 1st it goes to 10psi and at idle it is at 15psi is this ok
vacuum psi ???
- Thread starter Tommy91Stang
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93 LX
Founding Member
Well to start if you are not running a blower or turbo then you are not talking about psi, you are talking about inches of vacuum (hg). Vacuum is negative pressure and in a stock engine works like this. At idle your vacuum shoud be in the area of 15-20 inches. When you stomp on the throttle vacuum goes away and will head toward 0. As the engine speed goes up vacuum goes along with it. Normal cruise is 15 or so. The higher you can get the vacuum meter to read the better fuel mileage you will get.
93 LX
Founding Member
Well as high as it will go is the max for your engine. If you watch the gauge you will notice very little gas will cause the gauge to go towards 0. In a carbed engine you can get it close to 20 inches but I am not sute the max but it should be between 15 and 20.
