Poor mileage, loss of power, miss on one or more cylinders.
Spark plug failure,Spark plug wire failure,Vacuum leak,Fuel injector failure,
No, Diesels don not need a spark plug.
Yes, Edmond Berger created the spark plug although cars wer still experamental in those days.
Ford Expedition.
NO; it's there to stop stray sparks from burning down forests
Missing and or poor fuel economy. If the plugs have over 75,000 miles on them, just replace them. The same symptoms will occur with defective spark plug wires.
The resistance measured under low voltage conditions should be infinite. High voltage ... like that that produces the spark ... behaves differently.
The symptoms of a fouled spark plug are normally self evident in that the engine will loose power, run rough and use more fuel. Prolonged use of an engine with a spark plug in that condition will most certainly damage the catalyst convertor. Should renew the plugs and have an emissions test done to enure you are still complying with current regulations.
The ignition coil would only affect the spark to the spark plug(s).
Not enough information. What are the symptoms? No spark, Misfire?
You have a serious internal engine failure.
On older cars around 10,000v was needed. On modern cars it can be between 20,000 and 30,000 volts.