I am trying to figure out a 1999 dakota that hesitates, sputters, and putters most of the time. It is a 5 speed. It has had the plugs, cap, rotor and wires replaced. The throttle position sensor, O2 sensors have been replaced. The coil has been replaced. The fuel pressure is about 50 psi, at idle and during driving, so I do not think it is a fuel issue. Hot or cold, does not seem to matter. If you can baby it past the bad spot of sputtering and occaisional backfiring, it will run like a scalded cat. I just do not know this engine at all. Is there a most likely cause of something like this? THANKS

Is this temperature related or does it do this after it is up to operating temperature. Try getting some cleaner and cleaning the air control meter.
You can try using the plastic part of a screw driver and tapping if it runs better buy a rebuilt. They have a cleaner for this at the parts store.
Feel both the upper and lower radiator hose and make sure it is up to temperature. If it runs fine after reaching operating temperature ohm the temperature sensor.
Check the air intake system for bad leaking parts.

Temperature does not matter. Are you talking about the idle air control?

I was thinking chevy but I would clean the idle air control valve. I would also spray around the intake along the edges and around the injectors with carb. cleaner a bad intake leak will cause a rough idle and even stall an engine.
Also put a bolt in the hose to the vacuum booster as a leaking diaphram will also stall an engine. Don't drive this way just gun the engine.
If the carb cleaner hits a leak it will immediately smooth out. What I was talking about sits in the air nozzle between the air cleaner and engine.
Sorry for the mixup.

Ayup, sounds like a vacuum leak to me...or a stuck EGR or PCV valve...just a thought.

UNBELIEVABLE!! The answer is........ The upstream O2 sensor!! replaced it, and it runs like new.