I completed my engine (D16A6 replaced by ZC with intake from original engine) swap for my 91 CRX Si.

The engine fires and warms up. (seems to idle a little low, around 500 rpm; and maybe a little rougher than my D16A6. But, the guy I bought the ZC from said he put a bisimoto cam for a little more performance.)
Once it's warmed up, it will die at idle and won't fire without giving it gas.

My guess, so far Fast Idle Valve is functional. (the reason the car idles while warming up.)
and
Idle Air Control Valve isn't working correctly. (either electrical connection to it, the valve it self, or possibly both.)

A friend of mine said it could be the O2 sensor because that only starts working with the ECU once the engine is warmed up.

I should check the connection to the IACV maybe it got strained during all the shifting stuff around for the swap.

Another thing I'm considering is moving all the sensors/switches from my D16A6 engine block to the ZC engine block:
-2 prong above the oil filter(fan switch; does not seem to matter which wire is connected to which terminal)
-1 prong above the oil filter(oil pressure switch; working correctly)
-1 prong under the distributor(coolant temp sensor for the temp gauge in the cluster; working correctly)
-2 prong with plastic connector housing under the distributor (coolant temp sensor for the ECU; swapped the one from my D16A6 which was working correctly)
Maybe, one of these is bad on the ZC block.**

Any insight into fixing my idle once warmed up problem would be greatly appreciated.

Thanks,
Chris

**Note: Maybe, the fan switch on the back of the ZC is working correctly. But, the ECU sees that switch activate but doesn't see radiator's electric cooling fan kick in and either doesn't know what to do or cuts fuel to the injectors?