Sensor/System Checks

Use a scan tool to monitor the Knock Sensor (KS) system for excessive spark retard activity.
Check for throttle body tampering, excessive deposits, or damage.
Check the Throttle Position (TP) sensor and related circuits. See DTC P0122: THROTTLE POSITION SENSOR CIRCUIT - LOW VOLTAGE or DTC P0123: THROTTLE POSITION SENSOR CIRCUIT - HIGH VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 2.2L ION article.
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.