It would be great to have an electrical diagram for the OP to trace and confirm the wiring for the ovp.
This IACV thing seems interesting. Worth a try. So stick wires into the connector and read the voltage; also it will be helpful to know what the voltage should be and how it should behave.
Sent from my iPhone using Tapatalk
I do not have a circuit diagram PDF handy but here are the critical connections from my Haynes Manual:
OVP - Pin 30 to Battery positive terminal
OVP - Pin 31 to Chassis ground
OVP - Pin 15 to FPR pin 15
OVP - Pin 87 to ECU pin 1
Probably should also check the IACV connections to the ECU.
As for the average voltage on IACV, each car will be a little different because mechanically they are not created equal and also depends on system voltage. At idle they will start around 5V (cold) and drift down to around 4V average.
When the idle jumps to 1500 rpm confirm that IACV is zero (most likely OVP has cut off)
Right before stall, see if the IACV voltage jumps from zero to a positive value (most likely the OVP just woke up)
You can emulate this very malfunction by unplugging the IACV during idle and observe the idle increase to over 1000rpm. Then during idle plug it back in and observe the immediate stall.