Truck only idles when it feels like it

I have a 1981 Toyota pickup. when i start her. she starts fine, but sometimes she will idle fine, and then suddenly refuse to. it seems to be random. i can keep her running if i keep my foot on the gas just a little, to keep her rpm’s up. but have to put her into N and keep my right foot on the gas and my left on the brake to stop her when she refuses to idle. when she does this on the freeway, it just sputters and runs rough, but as long as i have the gas on, she keeps going. I don’t know what it is that regulates the idle to keep her going when my foot isn’t on the gas. also her serpentine belt is slipping. the one attached to the alternator, i can see her charge voltage dropping when she squeals her belt. that i know how to fix, but i’m wondering if it’s that, that is the issue? i was told that, but i don’t think her serpentine belt has anything to do with her idling. i was told how to raise her idle on the throttle cable and the Idle screw, but is there something else that regulates her idleing?

It has a feedback carburetor on it that is connected to a oxygen (O2) sensor. The O2 does not give you a check engine light when it goes bad, but those old ones usually had a two pin connector next to the distributor that you could hook up a voltmeter to to see if they were working. A bad O2 sensor would cause idle issues and poor gas mileage.

Other wise adjust the idle screw. There is a fast idle cam that the idle screw rests on when the engine is cold so if you are having trouble with idling when cold, the cam may be sticking.

“She” sounds like a typical female…