(12) United States Patent (io) Patent No.: US 6,925,982 B2
Surnilla et al. (45) Date of Patent: Aug. 9,2005
Primary Examiner—Bibhu Mohanty
(74) Attorney, Agent, or Firm—Allan J. Lippa
A method is disclosed for controlling operation ol an engine coupled to an exhaust treatment catalyst. Under predetermined conditions, the method operates an engine with a first group ol cylinders combusting a lean air/luel mixture and a second group ol cylinders pumping air only (i.e., without fuel injection). In addition, the engine control method also provides the following features in combination with the above-described split air/lean mode: idle speed control, sensor diagnostics, air/fuel ratio control, adaptive learning, fuel vapor purging, catalyst temperature estimation, default operation, and exhaust gas and emission control device temperature control. In addition, the engine control method also changes to combusting in all cylinders under preselected operating conditions such as fuel vapor purging, manifold vacuum control, and purging of stored oxidants in an emission control device.