Found solution for me here: Heroku + node.js error (Web process failed to bind to $PORT within 60 seconds of launch)

In my case my app crashed because I was hard setting the PORT, instead of using the port that heroku dinamicaly sets, which can be accessed with process.env.PORT

app.listen(process.env.PORT || 3000, function(){
  console.log("Express server listening on port %d in %s mode", this.address().port, app.settings.env);
});