My 99 Civic with mini me swap I've literally done everything to fix it and only code it has is iac, my question is will iac make car idle literally at 100 and make it very hard to start when it's warm

 

there is no one hundred.

 

Yes, if the IACV is not functioning, the idle will be very low... almost stalling... but it is actually under 500 rpm.

 

Test the IACV with an ohmmeter. If the coil is open circuit, replace IACV. If the valve is OK, check that the correct plug is plugged into it and that the wiring is OK. The code is telling you that there is an electrical problem with the IACV circuit. So I don't know why you went out replacing "everything else".

 

I had other things to fix which was wiring harness has a bunch of cuts and **** from previous owners and o2 sensor needed to be replaced bc it had a code for it, I'll check the wiring for iac cuz I've put countless iac on it and all of them do nothing but make my car die in traffic

 

Sounds like you are operating at base idle, (around 400). You need to get that IACV (Idle Air Control Valve) circuit fixed in order for your car to idle correct.