1. Monitor the Short Term Fuel Trim (SFT) reading, during cold engine operation, after closed loop is achieved, to verify the engine is running lean. Nurse carburetor cleaner around the intake gaskets to see if SFT readings can be driven down.
2. Check for swelled or leaking vacuum hoses. The Positive Crankcase Ventilation (PCV) hose is a common failure on these engines.
3. If no vacuum leaks can be found, check the Barometer (BARO) frequency on the scan data. If low, suspect a contaminated or bad Mass Airflow (MAF) sensor.
4. If BARO is normal, monitor the fuel pressure while driving. Fuel pressure should be 35-70 PSI, this is an electronic returnless fuel system and the pressure should be checked with a mechanical fuel pressure gauge while monitoring the Fuel Rail Pressure Sensor (FRP) on scan tool data. If the Parameter Identification (PID) is not found on scan tool data, use a voltmeter backprobed into the Red/Pink wire at the FRP sensor.