spark plug wire question

[tkgibbs27]

should any of the wires have any resistance to them at all?

[mvusse]

I used to always assume they had no resistance to speak of; like electric wires.

 

Turns out they do, like about 5000 ohms per foot or so.

 

Never actually tested for myself, so this is second hand information.

[tkgibbs27]

that is what my dad assumed, he figured it should be zero resistance. so we went and tested the old wires and we did notice there was a resistance difference in the lengths of the wires. we got around 7ohms on range 20k for the mid and longest length ones. about 6ohms on range 20k for the shorter ones.

 

we put in new plugs and wires today. the coil wire was definitely corroded. and it made a HUGE difference in how the truck rides now. it runs so much smoother. i took it up 40 to 50 at least six times since we did the tune up, and she has been running like a top. but i am going to give it a few days to see if she starts shaking again before i declare that the shaking is gone. i got my fingers crossed that it is.

[Eagle]

There is a resistance, but I don't recall what the spec is. The old FSMs used to give a number, but the new ones probably just tell you to hook it up to a scan tool. I think it was something like 1,000 ohms per inch or something like that. (Or maybe it was 1,000 ohms per foot?)

 

Resistance is needed to reduce radio interference. Most factory wires, in fact, aren't "wires" at all. They are fibers, impregnanted with a conductive carbon compound. Over time, as the wires get hot and cold, and maybe man-handled from working around the engine, the carbon gets broken and there are gaps that the spark can't jump. That's when you start getting skipping and missing under load.

 

The best replacement wires have a solid (or stranded) wire core, surrounded by a radio supprssion winding.