1st Dec 2011, 13:30
Of course it could be a bad spark plug, or a bad wire, or a bad rotor, or something else.
I would get a spray bottle with water, and when it is really dark, get under the hood. While the engine runs, I would spray water all over and look for sparks flying off the ignition wires and between them.
Next step, I would take out the plugs and inspect them closely. If any one looks suspicious, I'd replace all of them including wires, cap and rotor. Or if you have a coil pack, inspect the towers and electrodes inside the towers for any corrosion, cracks and deposits. When in doubt, replace them.
29th Nov 2011, 23:48
When you first buy any car, check the regular wear and tear parts, and tune-up related items. If they look original or of questionable age, replace them. This will save you headaches later on...