HIgh HC 99 civic si

[Antonio Chagolla]

Hello I been trying to bar my car but i keep getting high hc on 15 mph. When my car idles I checked my o2 sensors voltages and my downstream o2 sensor voltage fluctuates up and down from .015v up to 1v it follows the upstream sensor voltage. Only when I rev the car for a while the downstream sensor stops fluctuating and stays at about .7 volts. But after like a minute it starts to fluctuate again.