Spark Plug Wires

Synchros shot? Weird noises while shifting? Not sure what needs to be replaced?
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InlinePaul
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Spark Plug Wires

Postby InlinePaul » Sun Jul 23, 2017 1:00 pm

Our 1999 Plymouth Voyager was having hesitation and missing on take off, pretty much only at idle and would smooth out with rpms. Not running the AC helped prevent this but then it worsened. I took a shot at throwing parts at it, since the plugs had been replaced 10,000 mile ago (gaps were up to 75% larger than spec) I focused on the plug wires, which had about 40,000 miles on them.

I put new wires on and it runs like a champ. No more miss. Just ran the ohm meter on the old wires and got readings of around 3 to 5 among the old wires. That with the meter set to the 20k range. Googling tells me those are perfectly acceptable resistance for plug wires, so I wonder what was the problem. Perhaps a crack that leaks energy to the engine? I did not see any damage or cracks in the wires though. Perhaps the dielectric grease dried out and only needed to be replaced?
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theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...

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theholycow
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Re: Spark Plug Wires

Postby theholycow » Sun Jul 23, 2017 2:39 pm

Guesses:

- Flaky wire/connector

- Connector that doesn't connect well

- Passes test at room temperature dry, but maybe not when wet and/or hot
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Re: Spark Plug Wires

Postby Rope-Pusher » Sun Jul 23, 2017 10:03 pm

When the insulation breaks down, the Ohms might be the same, but the electricity leaks out to the air or to a path to ground just like a sprinkler hose. With high humidity or splashes of rainwater, this can diminish the spark energy enough that it won't spark a mixture at high pressure....like at low rpm and lots of throttle...cylinder pressure follows the torque curve.

I've driven a truck with leaky wires on a slant 6 engine and after driving through a puddle I could creep away from a stop, but not accelereate quickly away. Also, if I held it in low gear the engine miss was reduced as the rpms came up above the normal shift point.
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InlinePaul
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Re: Spark Plug Wires

Postby InlinePaul » Mon Jul 24, 2017 7:47 am

Ok, thanks. Guess I should not complain at 40,000 from a set of wires. It would miss even on initial cold start in the am. Odd thing is it was initially doing it worse in reverse. I think maybe that put more load on engine. Anyways, working great now. Guess we pitch those old wires and move on until the next problem arises.
Stick shiftin since '77
theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...


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