I'm trying to understand the contexts where this could be ok...
But it's important to notice that the Portuguese verbs "sair" and "ir" are different.
When we want to say "I have to go (away)", we use "ir": "preciso ir (embora)".
We only use "sair" when inside something, and really meaning to "get/go out" of that place. So, it could replace "tenho que ir" in a chat room, for instance, where "going" necessarily implies "leaving the room". It might be used in a meeting room, meaning "leave the meeting (room)".
Although both "must" and " have to" are used to express a strong obligation in English, there is a slight difference. "Have to" is used when some external circumstance makes the obligation necessary, whereas "must" expresses obligation imposed by the speaker. What about "ter que" and "precisar"? And "dever"?
eu preciso sair = I need to go out.
eu preciso partir = I need to go out (more poetic), I need to travel/go back.
eu preciso deixar = this sentence is incomplete. You always leave someone/something/somewhere. Eu preciso deixar esta casa = I really need to get out of this house / I can't take the house along with me.
Almost the same as the difference between "I have to go" and "I have to go away".
Embora "embora" pareça mais suave que "away". (Althoug "embora" seems lighter than "away"). - Sorry, couldn't help playing with words.
We use "ir" and "ir embora" interchangeably daily, but we need "embora" if it's going to never come back.