[V8] driveability problem

[John Dodd]

Today barely made it to work.When the temperature is low (-5 C and
lower) the idle fluctuates widely ,between normal and 200 rpm,the car
surges 
and has no power.At a light I placed it in neutral and rpm returned to
800 .Idles OK.So could it be that solenoid that controls the torque
converter ?
Problem is intermittent ,last time it happened was a month ago.Next time
when I start the engine it could be all gone.Unfortunately I don't have
a code reader.Thanks again guys.