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What should the resistance of the sparkplug wires be?

9.2K views 10 replies 6 participants last post by  TXFO  
#1 ·
Mine are are in the 5-9kohm range. I'll post exact values later on..

What's normal for a new set of OEMs?

Why do they give them resistance?
 
#5 ·
What's normal for a new set of OEMs?
I did some research awhile ago, on another (now defunct) Focus board, wherein I checked the resistance of OEM wires, FR wires, and LiveWires. Wish I still had that info.
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Why do they give them resistance?
I don't think it's a matter of them giving the wires resistance; it's that it becomes prohibitively expensive to make them exponentially less resistant. Whereas Ford might pay $10 for the wires they put on a stock engine, it might cost $30 to put really good, low resistance wires on the engine when it doesn't benefit the grocery-getting soccer-mom types who may buy the car. Now, SVT models probably get much nicer wires than the lowly Focus, and the same with other companies' tuner brands.
 
#6 ·
No... if it was a matter of cost they could just use copper in the wires. I forgot to answer the second part of his question. The resistance is there to stop interference with other engine sensors. A single pulse of high-voltage energy through a plug wire is basically like sending out an electromagnetic burst through a 1-2 foot long antenna. Using plain copper, you'd be likely to confuse the everloving hell out of your PCM, if not fry it as it picked up induced voltage spikes from sensors and wiring harnesses near the ignition system.

The resistance hampers the ability of the conductor inside the plug wire to be used as an "antenna" as easily.
 
#11 ·
The resistance is there to stop interference with other engine sensors. A single pulse of high-voltage energy through a plug wire is basically like sending out an electromagnetic burst through a 1-2 foot long antenna. Using plain copper, you'd be likely to confuse the everloving hell out of your PCM, if not fry it as it picked up induced voltage spikes from sensors and wiring harnesses near the ignition system.
just to expand, the only sensors that would really be affected by the "noise" would be the hall effect sensors. Unfortunately, these are the most critical ones.
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(crank, cam, VSS)

Ive heard of ultra low resistance wires interfering with garage door openers too.