What would cause the enginge to run rich and studder?

You may want to check the MAP (Manifold Air Pressure) located on the fire wall. There should be two rubber lines coming from it. Located just on the passenger side of the center. the temp sensor could also be the problem. its located near the thermostat. when the sensor is bad the computer is reading the temp as negative 40 degrees. its a little cheaper than a map sensor.