2004 Honda Civic SI ep3 cranks with no problem and fires up when cold but when it's been driven for a bit and heatsoaks on a hot day it most of the time refuses to start until it cools back down or I just get lucky.

New fuel pumopNew spark plugsNew battery (has no issue cranking when hot just starting)
no engine enginNew IACVnew alternator

 

is it not starting or just not cranking?

i had a similar problem with an old impreza i had that wouldnt start when it got hot out and it was the coolant temp sensor

 

Did you figure out the problem? Im currently having the same issue

 

its most likely the starter

try jiggling the key real quick back and forth when you start it, i can get it to hook when it does this