maybe your secondary air pump isn't pumping . Taken from webb; Secondary Air Injection (AIR)system,checking The Secondary Air Injection (AIR) system causes the catalytic converter to heat up more quickly,resulting in earlier operating readiness following cold start.Principle Due to overenrichment of the mixture during the cold start phase,there is an increased amount of uncombusted carbon monoxide in the exhaust.Secondary Air Injection (AIR)improves secondary oxidation in the catalytic converter and therefore reduce emissions. The heat produced by secondary oxidation greatly reduces start-up time for the catalytic converter,therefore improving exhaust quality during the cold start phase significantly.