It appears that you and I are in the same boat, trying to figure out our car`s woes. If could possibly be an OVP short. You should monitor the voltage/amps coming to the valve to insure it doesn`t have some sort of short, however unlikely.
I have been looking at the schematics and it appears that the main signal to impower the OVP relay comes from the ignition switch. In a prior post I read and restated that if voltage is present at the fuses in the OVP, it should be ok. From the diagram on the side of the relay, this is incorrect. It could still have an internal short or ground problem causing it to not put out the correct voltage to the fuel computer, idle valve or ABS brain.
Someone correct me if I am wrong.
Trying to figure it out for myself................cause I am cheap.