It's going to happen eventually.  Your Jaguar spark plug wire is going to need to be replaced.  Most commonly, the resistance in the wire will eventually wear down.  If this is the case, do not attempt to substitute non-resistant wires for the resistant wires you need.  Replacing the resistant spark plug wire with a non-resistant wire could end up damaging to your ignition system.  The insulation in your spark plug wire can break, causing cracks in the wire that leak energy to the engine body instead of sending it to the spark plug.  It's also common for your spark plug wire connectors to corrode.  The wire inside the insulation can break from the continuous vibration.  There are three major signals that your vehicle will give off when your spark plug wire needs to be replaced.  Those three signals are: miss-firing, hard starting, and poor fuel economy.  You can find a huge selection of wholesale priced spark plug wires at our online store.