Matthew Wright explains on About.com that one possible reason for an engine surge is that the choke on the carburetor may not be set correctly, or it may not be working properly. In this case, the solution is to check the choke plate and ensure that it is opening completely.
The engine running too hot could also result in surging or misfiring, Wright states. In this case, assessing and repairing the cooling system should resolve the problem. If surging is due to the fuel pressure regulator operating at unusually low pressure, the pressure should be checked with a fuel pressure gauge. The regulator may need replacement. If the surge is due to an incorrect ignition timing setting, the timing should be adjusted. Another common cause of engine surging is a faulty ignition system. The distributor cap, rotor, spark plugs and ignition wires must be checked and replaced, if necessary.
Wright adds that the computerized engine control system could be faulty. It is important to check engine control systems using a scan tool, and test circuits and fix or change components as required. Replacing components is generally not a do-it-yourself task. The repair should be made by a professional auto repair shop.