Sensor/System Checks

Check the air intake system and crankcase for air leaks.
Check the Positive Crankcase Ventilation (PCV) system for proper operation. See POSITIVE CRANKCASE VENTILATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTS - 2.2L ION article.
Use a scan tool to monitor the Knock Sensor (KS) system for excessive spark retard activity.