Sensor/System Checks

WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Check the Positive Crankcase Ventilation (PCV) system for proper operation.
Check the throttle body, and Throttle Position (TP) sensor for proper operation and damage.
Check the Knock Sensor (KS) system for excessive spark retard.
Check the Exhaust Gas Recirculation (EGR) system for proper operation. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4.0L AURORA article.
Check the Idle Air Control (IAC) valve and valve housing for deposits and/or damage.
Check for dirty or damaged air cleaner element.
Check for collapsed or damage intake air ducting.