Not much to go on there. I would look to see what the voltage range of the ignition is. I think you are at the lower end of the range. Eneloop cells are also a low discharge cell. I would try a 2s lipo battery unless for some reason you have an older ignition. Fuel filters are also very important on gas engines, I consider them a must. Hobby filters don't filter well enough IMO, I hit the garden and lawn equipment department in the hardware store for filters. I also recommend running a felt clunk and filling the tank through a third line. At the end of a flying session keep a couple ounces of fuel in the tank. This keeps the flexible parts in the carb from drying out and becoming stiff. Even with that if my engine hasn't been run in a few months, I will fuel up, run at a high idle until fully warmed up and then let it sit for a 1/2 hour or so to let the new fuel soften up the carb flexible parts.