It sounds like a weak spark to me. If the coil is weak, or the plug is dirty or even if the gas is old it might do that.
Might be worth checking the whole ignition system. I would check with a vom to see if you are getting a full 12v the coil.
Might be worth checking the whole ignition system. I would check with a vom to see if you are getting a full 12v the coil.