My Grandson Has Been Running A Fever Since Wednesday I

My grandson has been running a fever since Wednesday I took him to ER Wednesday and they did not find the reason for the fever but it was extremely high then 104.2 it has not gotten they high again and have been giving him Tylenol and Motrin every 4 hours and it comes and goes I will check it in four hours and no fever but I check it a few hours later and its beck 101.4 somewhere around that temperature should I take him back?