Hesitation, Sag Or Stumble: Sensor/System

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Pontiac Grand Prix, 2003 Pontiac Bonneville, 2003 Chevrolet Monte Carlo, 2003 Chevrolet Impala, and 2003 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

Check the following items:

Check the Heated Oxygen Sensors (HO2S). A HO2S should respond quickly to different throttle positions. If not, inspect the HO2S for silicone or other contaminants from fuel or use of improper RTV sealant. The sensors may have a White powdery coating. Silicone contamination causes a high but false HO2S signal voltage (rich exhaust indication). The Powertrain Control Module (PCM) will reduce the amount of fuel delivered to the engine, causing a severe driveability condition.
Check the Throttle Position (TP) sensor and related wiring.
Check the Mass Air Flow (MAF) sensor and related wiring.
Check the Exhaust Gas Recirculation (EGR) system for proper operation. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.