yup, most likely the idle valve not in good condition. Yes, I'm aware that ECU need feedback from O2 sensor. I bypass the O2 sensor temporarily before get a replacement. If I connect the O2 sensor, the idle is very bad. Sometime the engine stall.i admire this car.. better check the throttle body. might be idle control valve gone. or maybe the hose u need to connect back. u cant disable the 02 sensor as the ECU might not reading well.