High Idle Question

[WAFI]

Is there any chance that if the Standby Vacuum was pulled, would cause a slightly higher idle? 

 

[ShuRugal]

How much is "slightly" and what is your source of standby vacuum?

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[WAFI]

200 rpm and I’m not really sure the source yet. I haven’t looked any further into it yet. Just wondering if it could cause such a thing. 

Also, I have just removed all my vacuum driven gauges but haven’t removed the vacuum system yet, just plugged the lines for now.

[ShuRugal]

if your stanby vacuum source is pulling manifold vacuum, then you would see a small rise in RPM with it applied, especially if all your vacuum instruments have been removed.  That lever would basically function as an intake leak.  You would probably also see the engine get leaner, if carbureted.

by 200 RPM?  not sure, depends on how big the orifice is to draw vacuum, but it's certainly not impossible.

[JoeM]

My standby vac is from the intake manifold and it causes idle to increase about 150-200 rpm when pulled. 

[AIREMATT]

Just removed my standby vac system as PCS is the only thing left vacuum powered. Need a new tube where the saddle clamp penetrated it but didn’t take much else and only changed about .75 pounds total wt.

It did Eliminate the repetitive AD on the testing of it at Annual too.

[WAFI]

Nice, I'm going to look into it this afternoon. I think the cable is stretched or faulty but I'm going to just have it removed. 

[WAFI]

CONFIRMED- all fixed now.

I pulled my cowling off and there it was, stby vacuum valve was wide open with the cable pulled out. Closed the valve and she idle perfect again. 

[carusoam]

Great follow up Wafi!

Any extra air getting into the intake can be similar to the butterfly valve / throttle opening….

Nice catch!

Best regards,

-a-