I bought plug wires (cap and rotor too) for my '95 F150, 300 I6. I got Motorcraft and after installing them saw an extra wire. It looked like an alternative coil wire, but with a different connector. Anyway, having that laying around I decided to test it's resistance as representative of all the new wires. It was 5,000 ohms and 14 inches long (about 4300 ohms per foot). Then I tested the old wires that were used 20,000 miles ago when I bought the truck. They tested out to around 1000 ohms per foot (They are "Triple A Silicon"). What gives? The Chilton manual says max 5000 ohms per foot for the '87-'88 (I don't have the newer manual) and another book says the resistance is meant to be there and vehicles are made to run with the resistance. Truck seems to run better, but runs at least as good as before.

1) Did I replace a high performance wire set with a stock OEM set?

2) Did I get a faulty set?

3) Does it run better with the higher resistance OEM wires because it is designed to run with them?

4) Other (please explain)

At this time, since it runs fine, I am inclined to leave well enough alone, but if the OEM wires are so close to the spec maximum resistance, how long will they last?





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Not too sure what to tell you. I know that when I replaced the plugs and wires on a '92 Tempo there was an extra wire there too. Kind of looked like it went from the distributor to something else nearby but I didn't know that much about it so I didn't wanna mess with it. Something that I thought about a while back though is that some sets of wires are universal sets and so its possible that on some engines you'll need two wires same length rather than each one different. I really don't know. Good way to find out if the old wires were performance ones or not is look to see if they wires are numbered. If they are, they are stock. If not, could be performance then. Other than that, don't know what to say. Sorry couldn't be of much help to you. Goodluck though.

James

 

Mr Tallpaul, I think you already had hi-po wires on there, with the 1K ohms per foot. Generally speaking, the lower resistance wires, the better. Up to a point. You cannot run solid core wires (near 0 ohms), on an electronic ignition. The solid cores will transmit "flyback", which is a type of electrical feedback that occurs when the sparkplug fires. This flyback is "resisted" by the resistor wires before it can reach the ignition electronics, and cause misfires.

I installed a set of solid core Mallory wires on my Jeep (with electronic ignition) a couple years ago. On the test drive, I barely made it back home because it missed so badly. I then put the stock coil wire back on, which had about 5K ohms. This effectively gives me 5K ohms resistance to all the wires. The Jeep has run great ever since.

If the truck runs OK, I would just leave the new wires on it. Save the old ones, though. They are probably still good.

 

Guess I could put the old wires back on, provided they have good insulation. My research indicates one should observe the wires with the engine running in the dark and look for sparks off the wires. Also spraying water on them helps this diagnosis. If they pass that test, then a resistance test, they are still good. Guess I should have done my research before gettting the wires. Anyway, the cap and rotor were due for replacement with obvious erosion of the contacts.

 

Ever since changing the cap, rotor, and wires (plugs only have a few thousand on them) my fuel mileage has consistently been 17.5--and I have a heavy foot! I was getting around 16 to 16.5 before.

 

I was taught in school that resistor wires should be aprox. 5,000 to 6,000 ohms per foot.

kmichaelb

 

Thanks Kmichaelb, It seems that the system was designed for the resistance wires and to change over to low resistance wires should involve changing other components of the ignition system to be compatible with a low resistance wires. I don't see the need as the truck runs great!

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