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.
August, 16, 2011 AT 2:02 PM
Truck starts fine but when I step on the gas it hesitates like it's not getting enough fuel. Have changed all sensors except o2. Still have black smoke coming from tailpipe so will check the above. Could this be a fuel pump problem?
August, 16, 2011 AT 11:09 PM
Check the fuel pressure with a gauge if its within specs-Injector/s and fuel pressure regulator could be leaking-investigate