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They are important, more so with injected engines, carbs/reed engines will burn the water (small amounts) it will steam and decarbonizes the engine also. all though I don't recommend water in fuel. look at the fuel filter under the bonnet if it has one. When this happens it will miss a beat or stumble a bit and resume, kind of a sputter.
Run the engine at night in the dark to see if there is a short in the plug wires(maybe moving them around while running) At night or in the dark it is easy to see if there is a problem if something is grounding out. Others will have other ideas also.