I just replaced the water pump and the thermostat but my temperature is still fluxuating(sp). I just can't keep the engine in the normal temp range. Any ideas what the problem is?

 

If there are no signs that the engine is actually overheating and the gauge is fluctuating when it has no reason to, I suspect the temp sending unit is bad.

On most motors it screws into a water pasage on the intake manifold. When it goes bad, it is sending unreliable information back to your dashboard gauge. Should be cheap and easy to replace.

 

Make sure you have all of the air out of the system. If an air pocket forms where the sender is, the temp will swing big time.

 

I had a similar problem with my '96 F150 4.9/5sp. I changed the water pump, thermostat, radiator cap, flushed the system, and the temp sending unit. I finally replaced the fan clutch and that solved the problem.

Good luck.