Diagnostic Aids
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 for the following conditions:
- High resistance in an IAC valve control circuit.
- The correct Positive Crankcase Ventilation (PCV) valve, properly installed and proper operation of the PCV valve.
- Proper operation and installation of all air intake components.
- Proper installation and operation of the Mass Airflow (MAF) sensor, if equipped.
- A tampered with or damaged throttle stop screw.
- A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
- A skewed high Throttle Position (TP) sensor.
- Excessive deposits in the IAC passage or on the IAC pintle.
- Excessive deposits in the throttle bore or on the throttle plate.
- A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve See SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
- If the problem is determined to be intermittent, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.