Rough, Unstable Idle
- Check for sticking or binding TPS or throttle linkage. Check idle speed and IAC system. See CODE 35 CHART in COMPUTERIZED ENGINE CONTROL section.
- Verify alternator output voltage is between 9 and 16 volts. Repair as necessary. Check P/N switch circuit (if equipped). Check ECM ground circuits. Check EGR system and PCV valve operation.
- Perform injector balance test. See appropriate C-2A INJECTOR BALANCE TEST in COMPUTERIZED ENGINE CONTROL section. Check ignition system and ignition timing. Check fuel evaporative system. Ensure battery cables and ground straps are clean and tight.
- Check A/C input to ECM. Check for vacuum leaks. Check for loose or damaged air duct between MAF sensor and throttle body. On 2.8L VIN S, 5.0L and 5.7L, check Air Injection Reaction (AIR) system. No air should exist at ports during closed loop operation.
- On all models, inspect O2 sensor for contamination from fuel. Sensor is defective if coated with a White powdery coating. Disconnect MAF sensor. Replace sensor if condition is corrected.
- Check for fuel in pressure regulator hose. Replace pressure regulator if fuel exists. Check cylinder compression.