Diagnostic Aids

Inspect for the following conditions:

• High resistance in an IAC valve control circuit.
• The correct 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 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 TP sensor.
• Excessive deposits in the IAC passage or on IAC pintle.
• Excessive deposits in the throttle bore or on the throttle plate.
• Vacuum leaks.
• A high or unstable idle condition could be caused by a non-IAC system problem that cannot be overcome by the IAC valve.
• For intermittent conditions, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.