even with the ISV disconnected/not working the car should still idle of the idle screw on the throttle body when up to temp - though it struggle to idle when stone cold
ISV is the small electrical cylinder beside number 4 inlet runner, just infront of dizzy. with the ignition turned on, feel the ISV it should be buzzing. if it aint then thats your problem
check the wiring & sender for it, green & red wire beside water outlet below dizzy. you can swap it over with the red/yellow wire or blue/white wire senders to test