Diagnostic Aids
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Inspect for the following conditions:
- A high resistance in an IAC valve control circuit.
- Correct PCV valve, properly installed and properly operating.
- Proper operation and installation of all air intake components.
- Proper installation and operation of MAF sensor, if equipped.
- Tampered with or damaged throttle stop screw.
- Tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
- Skewed high TP sensor.
- Excessive deposits in IAC passage or on IAC pintle.
- Excessive deposits in throttle bore or on throttle plate.
- Vacuum leaks.
- High or unstable idle condition, could be caused by a non-IAC system problem that cannot be overcome by IAC valve.
- If the problem is determined to be intermittent, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.