I have a 91 civic with a 94 gsr, running obd1. o2 sensor is not plugged in(harness is cut). My ecu has o2 sensor off but it runs/idles like **** under3k rpm. When i turn the car on, it idle fines for like 10 seconds then it as a lumpy idle and bogs. Could the o2 sensor not plugged in be causing this?