What year, what engine & how many miles? What have you done to correct the problem thus far? Change thermostat? Did you back flush the heater core and is there sufficent flow? Are the doors in the air passages opening and closing properly? After you've done everything else last resort is new water pump because the blades have a way of wearing way down.
Surges - Sounds like the MAF, mass flow air sensor, might need cleaning and dump in a can of Sea Foam available at auto parts stores.
http://www.seafoamsales.com/motorTuneUp.htm