Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2001METRO L4-079 1.3L VIN 2 MFIREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSRELAYS AND MODULES - COMPUTERS AND CONTROL SYSTEMSIDLE/THROTTLE SPEED CONTROL UNITDESCRIPTION AND OPERATIONENGINE IDLE SPEED CONTROL OPERATION
2001 Chevrolet Metro L4-079 1.3L VIN 2 MFI
Engine Idle Speed Control Operation
2001 Chevrolet Metro L4-079 1.3L VIN 2 MFISECTION Engine Idle Speed Control Operation
The engine idle speed is controlled by the Powertrain Control Module (PCM) through the Idle Air Control (IAC) valve. There are several reasons for idle speed control:
1. Maintain the engine idle speed at the specified RPM at all times. The engine idle speed can vary due to any of the following reasons:
^ A change in the load applied to engine (when an electrical load is applied, the automatic transaxle is shifted to R, D, 2, or L ranges, the A/C is turned ON, the headlights or stop lights are turned ON, etc.)
^ A change in the atmospheric pressure
^ A change in the engine's condition over time
2. Improve the starting performance of the engine
3. Improve the driveability of the engine during warm up
4. Compensate for the change in the air/fuel mixture ratio when decelerating (dash-pot effect)
1. Maintain the engine idle speed at the specified RPM at all times. The engine idle speed can vary due to any of the following reasons:
^ A change in the load applied to engine (when an electrical load is applied, the automatic transaxle is shifted to R, D, 2, or L ranges, the A/C is turned ON, the headlights or stop lights are turned ON, etc.)
^ A change in the atmospheric pressure
^ A change in the engine's condition over time
2. Improve the starting performance of the engine
3. Improve the driveability of the engine during warm up
4. Compensate for the change in the air/fuel mixture ratio when decelerating (dash-pot effect)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.