2nd Gen Ram Tech1994-2001 Rams: This section is for TECHNICAL discussions only, that involve the 1994 through 2001 Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.
It has no codes, the O2 sensor is OK.
When I bought this truck about a month ago I put new spark plugs, air filter, coil, and cleaned the injectors, cause it was hard to start, right now is still sometimes hard to start (is the same cold or warm) and today blowin some black smoke, could it be the distribuitor???
Put a fuel pressure gauge on it. Turn the key on, (might have to cycle it a couple times) to build fuel pressure. Watch how fast it bleeds off after the pump stops. If pressure drops quickly.... you have a problem. At that point, you would need to pull the fuel rail with the injectors to see just which ones were bleeding down. (or, if it was just a pump check valve issue....)
If it isn't the injectors, I would be looking REALLY hard at the coolant temp sensor.