How do you know when you need new spark plug wires? I searched and there was no indication as to "when" they need to be changed. Any help would be great.

 

I know I've read somewhere that there should be no more than 1 ohm of resistance per foot of ignition wire. If you don't have an ohm meter (multi-tester), you can get one from harborfreightools.com for under $10. My personal experience tells me that I should have replaced mine before they got to 1 ohm resistance per foot. I replaced my original Nissan wires at about 160,000 miles. The difference in throttle response with the new wires was quite noticable.