Vacuum Sphere of Mystery?

[DWCaprice2017]

Hi, All!
This is Daniel, with the '84 Caprice, 305 engine, Quadrajet carb.
I've been told by very knowledgeable members to check the vacuum hoses for solid connections
in case a vacuum leak is causing the rough low idle. As I looked around, I found a hose y-connector that
goes to the "Sphere of Mystery", located above the charcoal canister. In the closer photo, you can
see where a missing hose goes. What does the other end connect to?
And what is this thing?
Does it have something to do with the cruise control (which doesn't work)?

 

[383_StealthRam]

Should be the vacuum feed from the intake port off the back of the intake manifold, behind the carb?

 

[Ugly1]

That is a reservoir for vacuum. If you have an A/C system or something that needs more constant vacuum rate it is added. It is a good thing for an engine that produces low vacuum due to the cam lope as well. Most of your Caprice/ Large vehicles ( trucks/ Blazers)had them.

 

[DWCaprice2017]

Thank you 383_StealthRam and Ugly1 !
I'll look for a hose at the rear--hopefully being able to find it!
I know the computer control on the electronic Quads makes them more fuel efficient,
but did they have to be so dang complicated?!
I know that a couple years later they went to fuel injection, too bad they did use that
in '84!

 

[Ugly1]

Thank you 383_StealthRam and Ugly1 !
I'll look for a hose at the rear--hopefully being able to find it!
I know the computer control on the electronic Quads makes them more fuel efficient,
but did they have to be so dang complicated?!
I know that a couple years later they went to fuel injection, too bad they did use that
in '84!

You should be able to find the vacuum hose diagram online or even here in the information threads. Be carful that the one you look at on line matches. I just did it. With my Cadirat. Yeah the TBI was just starting out in a limited amount of the cars then. Firebird,T/A,Camaro,maybe the S10’s.
You may have to call it “Emissions Vacuum line diagram” to get it. If you can’t come up with it ask the local Chevy dealer (praying) they can print one out. If that doesn’t work check your local salvage yard and see if they have a junker to look at.

 

[Ribbedroof]

Once again, OE shop manual is worth it's weight in something for diagnosing these sort of problems. Can usually find printed ones cheap on ebay or order the printed or CD versions multiple places

 

[Ribbedroof]

 

[Ribbedroof]

Also, that looks to me more like an elbow than a Y. Does it have a hole through the "missing" leg?

 

[MrSony]

Single port ball is for cruise, two port ball is for hvac controls to switch vent modes.
The one pictured is for cruise. You need a manifold vacuum source with a check valve for it to work properly.

 

[Ugly1]

Single port ball is for cruise, two port ball is for hvac controls to switch vent modes.
The one pictured is for cruise. You need a manifold vacuum source with a check valve for it to work properly.

Think that was in his second pic. So you were on a he money!