If that is the problem, see my post #16 of 2019 - two years later, still no surging so I guess replacing the oil temperature sensor located down near the oil filter on the 4.4 V8 was the solution.
Replacing the oil temperature sensor did not cost much and was pretty easy to do - yes, that is unusual and hence worth a try if surging is the concern you have.
Well I have the same surging RPMs problem (accelerator pedal stationary, car speed constant and RPMs bounce up and down when engine is cold) and I replaced the sensor per your suggestion bbyer. Unfortunately doesn't seem to be the cause in my case.
Aside from the coolant temperature sensor in the thermostat any other suggestions for parts to through at it? 2005 SE V8 120k miles and it maddening frustrating.