The misfired and uncompleted burned cycles increase during the preliminary process and the ignition delay is longer than warm start during transient process, so the HC and CO emissions rise.

• 冷机起动初始期失火循环和燃烧不完全的循环以及过渡期滞后燃烧循环较多，导致这两个阶段的HC和CO排放明显升高。