Idle speed fluctuates (MIL works OK, no DTCs set)
Diagnostic procedure
  1. Do the ECM idle learn procedure.
  2. Test the fuel pressure.
  3. Test the injectors.
  4. Troubleshoot the alternator FR signal circuit.
  5. Inspect the PCV valve.
  6. Test the throttle body.
Also check for
  • Fuel contamination
  • Intake vacuum leaks