Rough, Unstable Or Incorrect Idle & Stalling: Sensor/System
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
- Check for conditions which cause an incorrect idle speed:
- Throttle body tampering, excessive deposits, or damage.
- Restricted air intake system.
- Large vacuum leak.
- Check the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the Mass Airflow (MAF) sensor and the throttle body.
- Check crankcase ventilation valve for proper operation.
- Check the Throttle Position (TP) sensor and related wiring. See DTC P0123: THROTTLE POSITION SENSOR CIRCUIT - HIGH VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article.
- Monitor the 24X crank sensor and the Camshaft Position (CMP) sensor signal present parameter on the scan tool. If both are not responding, test the sensor feed circuit. Both sensors use a separate feed circuit but are internally connected to power. Check all CKP sensor "A" and CMP sensor circuits for intermittents. See INTERMITTENTS .
- Monitor the 3X parameter on the scan tool. If the 3X is not responding, check the CKP sensor "B" and circuits for intermittents. Check the Ignition Control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open, or shorted may not set a DTC immediately, but are capable of causing driveability complaints. See INTERMITTENTS .
- Check the Exhaust Gas Recirculation (EGR) system for proper operation. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
- Check the transaxle range switch input with the vehicle in Drive and the gear selector in Drive or Overdrive.