Schantin

iTrader: (6)

Here's the deal. Have a mechanical Autometer vacuum/boost gauge hooked to an intake vacuum line for my STS turbo. Under load and under positive boost.....gauge is rock steady.

Under VACUUM the gauge sometimes oscillates; usually when at 20 inches of vacuum or more. I notice it most when idling or coasting with my foot off the gas. When applying load to the car (i.e. pressing the throttle) I don't see an oscillation.

So, is this normal, or a symptom of some other problem?

It's annoying at times if nothing else. I monitor the gauges like a hawk with this FI.....so input is appreciated.

Thanks.

anarchy99

iTrader: (7)

Vacuum leak? Taking a shot in the dark here.

TIM Z

iTrader: (12)

mine does not do that, its just a Faze boost gauge. make sure you dont have any teflon tape or sealent gumming up the hole on the back of the gauge where the line hooks up.

John_D.

iTrader: (2)

A long time ago, a vacuum gauge was used to diagnose engine problems. A fluttering vacuum at idle could indicate a misfiring cylinder, sticking valves, etc.

You are probably just seeing a little reversion in the intake from the cam. Which goes away when you have the throttle opened a little and more air flowing through the intake.