Rough, Unstable Or Incorrect Idle & Stalling: Sensor/System
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.
- Check for conditions which cause an incorrect idle speed:
- Throttle body tampering, excessive deposits, or damage.
- Restricted air intake system.
- Large vacuum leak.
- Inspect 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.
- Inspect crankcase ventilation valve for proper operation.
- Check the Throttle Position (TP) sensor and related wiring. Go to DTC P0123: THROTTLE POSITION SENSOR CIRCUIT - LOW VOLTAGE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.
- Monitor the 24X crank sensor and the CMP sensor present parameters 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, inspect the CKP sensor "B" and circuits for intermittents. Inspect 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
- Check the Exhaust Gas Recirculation (EGR) system for proper operation.
- Inspect the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.