My car is Toyota AE 100 and year 1991. When I start the car it gets 900RPM. But while I'm driving it gets 1800RPM as Idle RPM. (When gas pedal is released and held clutch pedal). Sometime it works normally. Then vehicle idle RPM is not steady. It may differ from 900RPM. I want to know that it is the problem of throttle body sensor or ECU. How I can solve the problem. I asked form several garage but they were not able to offer me better solution. Please help..! thank you