I always thought you had to use the "Jump Test."

You know, you keep the engine running and you grab the wires. The higher you jump the sooner you have to change the wires.

 

I had a shudder at high speed, quite some time ago. Turned out to be a fouled plug/wire. Ford dealer replaced it just out of warrantee for a freakin $330cdn!!! Check engine light came on too. I think it was around 50k kms but I could be wrong. Have 82k now.

Most plug wires are carbon core. The spark energy basically travels through some fiberglass cord impregnated with carbon power. Over time this powder disintegrates and your spark energy either has too much resistance to give 100% to the spark plug or it grounds out through a fault sheath to your engine block or other grounded components.

With the high mileage we get from the first set of plugs it's best to change the wires too, while you're under the hood.

I've been looking for a nice THICK 9 or 10mm performance wire set for the 4.6 but can't find anything decent yet. Nothing from msd, accel or taylor that's true performance wire. What's going on? Will a Mustang set fit on my truck? (1998)

 

Wires arnt something that has to be replaced frequently. If you think your responce loss if from that area, check your plugs first, and when changing those, i recomend Motorcraft, or AutoLight. Make sure all of your boots are on tight, on your plugs ,and distributer. Check your distributer, make sure there isnt any carosion in it at all. And then if those are fine, and your bored one day and have some money just laying around, then you can go ahead, and get some new wires, and see if that does the trick.

 

While that is a valid arguement, keep this in mind: The best ignition system in the world won't do much good if the power can't get to the plugs. Wires are worthy of more concern than that, IMO.

Take care,
-Chris