Écoeurant in Québec is different from France's definition. In France, it has a negative connotation
no matter what. Écoeurant in France would be the equivalent of "to cause vomitting" or simply "disagreeable" (i.e., not cool).
As you might've already known, the word comes from "coeur" which is heart. "Avoir le mal de coeur" is an expression for being sick and wanting to vomit. It literally means "Having heart pains", which kind of makes sense, because when you want to vomit you have that stuffy feeling in your heart.
In Québec, it may have several meanings depending on its context.
Ton bicycle est écoeurant!
Your bicycle is awesome!
Arrête de m'écoeurer!
Stop annoying me!
Tu as eu des billets pour Pink Floyd? Mon écoeurant...
You got tickets for Pink Floyd? You lucky bastard...