Cold Start Idle Control System Performance
During the cold-start phase the ECU runs an elevated idle speed and a richer mixture to bring the catalyst above light-off temperature quickly. The cold-start idle does not behave as commanded - speed sags, hunts, or fails to come up. Possible causes are intake leaks active when cold, an IAC valve sticking, or implausible coolant temperature.
Affected components
- Idle air control valve
- Cold start strategy
- Intake manifold seal
Common causes
- High likelihood: Intake leak only when cold (gasket shrinks)
- Medium likelihood: IAC valve sticking when cold
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.