I would clean out the ISCV anyway(& TB too myself), then start by setting the idle. With the engine @ norm opp temp & ISCV dissconected, set the revs to 725 ish rpm, reconect ISCV, & leave to idle for 10-15 mins, no reving/blipping! for ECU to relearn new idle values. If NG, try dissconecting the speed sensor wires (3 pin plug leading to speedo drive) If ok, replace sensor.