1999 chevy 4.3 truck starts up cold but if you give it a little gas its missing and smoking runs great after warm up I have changed fuel pump cts sensor complete tune up fuel injector cleaner and map sensor and I did a computer analysis and shows no code
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.