Check the fuel pressure if its within specs if not could be the injectors leaking, fuel pressure regulator or a clogged return line-
Probable causes of an engine running rich are as follows:
1. Excessive fuel pressure can be cause by restricted fuel return line
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.
Thursday, May 17th, 2012 AT 3:11 PM