hose attached to carburetor

[dr. d]

hi guys, im new with 4 wheels. i have a 4k engine on my owner type jeep, i have a question on what is the purpose of this hose attached to my carburetor, it seems like if i pulled if off, there is a very big difference on the idle, if unplugged it will cause a very low idle and the engine will stop, so i have to turn the idle screw a little bit to make the idle higher, im asking because i've been using this owner type jeep with this hose not plugged in, and someone noticed that it should be plug in to the carburetor.

what is the purpose of that hose? obviously it doesn't contain fuel in it.

the hose is pointed with yellow arrows attached form a device going to the carb.. what is that device encircled in yellow?

image attached below:

that's the mechanical advancer mechanism. the rubber hose from the carburetor is connected to the throat of the carb. at high engine revs, air pressure in the throat decreases, changing the pressure on one side of a metal diaphragm in the metal gadget on the left, causing the diaphragm to move. the movement of the diaphragm actuates a metal arm that connects to the distributor. the back and forth movement of the metal arm causes the distributor mechanism under the plastic distributor cover to rotate a little. this rotation movement causes the ignition timing to advance a little when the engine revs, and goes back to idling timing when the engine slows down to idling. when there is an air leak anywhere in this system, your distributor ignition timing won't change with increasing rpm, resulting in diminished engine pulling power. this leak can be remedied temporarily by fiddling with the carburator idling screw.

the shortened version: that's the mechanical advancer mechanism. it is connected to the distributor by a metal arm. it is actuated by the carburator's throat air pressure, as transmitted by the rubber hose. changes in the throat pressure, as dictated by engine revs, results in a change in ignition timing (higher rpm, lower carb throat air pressure, advanced ignition). this change results in better utilization of the expanding gases of the burning fuel.

when there is a leak in the system, or when the carb connection is blocked, mekanikos have learned to resort to simply increasing the idling rpm, or advancing the ignition timing permanently, so's their engines can be more workable..
repairing the system is easy. the advancer is cheap. so's the rubber hose. and the blocked air passage can be cleaned with relative ease. have yours repaired, and you'll be amazed at what you've been missing..