diognos this problem if you can.. my sisters car on 2004 Kia Sedona

k i stopped it from over heating,but now it is losing power, so what can it be. i know maybe the coil pak may be the problem but i sure hope this is the problem cause i can not figure anything else out.when i drive t, it has good power at first then it looses it power after it is getting warmed up.. my nephew is trying to fix it but i don't know what the problem is...

Asked by for the 2004 Kia Sedona