Fuel milage and performance will drop. The car may "stutter" and will not idle or run smoothly. If the plugs get bad enough. The car won't be drivable.
No, that will have no effect on the battery.
If there is a question about it, replace it. They are not terribly expensive. If the plugs are starting to go bad, replace them all. And the spark plugs wires too. An ounce or prevention is worth a pound of cure.
Yes.
It is possible but for all the plugs to go bad at the same time is unlikely.
Yes, along with many other things.
If you dont know how to replace spark plugs I recomend you go to someone that does and have him show you because you might do more bad then good trying to change them for the first time.
Yes a bad spark plug will make your car shake and when my truck had like 4 bad spark plugs it wouldnt wana go over 60. To test if you have bad plugs unplug the wire from the one you think is bad. Also the engine light might come up and when you take it somewhere like auto zone abd run the numbers it might say misfiring on cylinder xx.
Ecu is probly it the chance that two coils to go bad at the same time is not likely yet possible
Go to Auto Zone and they will check you engine light for FREE... And go from there...
Ummmm......... I think you want to use spark plug wires.
It is best to go with the factory used spark plugs. The factory uses champions.