Hi,
I have been running for the last 8 months with the engine light on (catalyst eff low...) I was just leaving it as the Cat is new, the O2 sensors are new, the exhaust is new and the 96 Civ runs great and gets 35 mpg...I have cleared the code during that time only to have it come right back on within 10-20 miles. Now it has finally started getting warmer around here and the light suddenly turns off. While I am driving it during the warm day 70F+ is was off. Then the weather cooled a bit (50F+) and the light came back and has been back since. There is no real noticable difference in the car's performance. I notices there is a regular slow pulse during warm days at idle (like a moving govener on a lawn mower) but it runs smooth, does not stall and still gets the same mileage. Is there anything about the cooler vs warmer ambient temperature that could trigger this light?

Maybe I watch too many CSI shows but there is usually a clue burried in the details...

Thanks
KR