how long do plug wires last

[MrShorty]

I changed the spark plugs and wires when I bought the truck. Now 30K miles later, Ford recommends that I change the plugs as maintenance. That's fine, but I'm wondering, do you change your plug wires everytime you change your plugs, every other time, or how often?

 

[Alec]

In general, plugs and wires every 60k miles.

 

[Opera House]

I have yet to ever replace a set

I did replace a coil to distributor lead once because a piece of metal wore through it. I do wash and ohm them out on occasion. It is probably just easier for most people to replace them if you don't know what you are looking for. I just can't remember ever replacing a wire set in 30 years. My 92 has well over 200K on the factory set.

 

[BradE.]

What kind of plugs did you replace them with when you got the truck? Unless they are Copper plugs they should be OK. Take em' out and look at them.

As for wires, I just replaced mine last week and they had 83K miles on them.

 

[MrShorty]

Along the line of "stock plugs in a stock engine", I did put copper plugs in. (The owner's manual calls for copper plugs (motorcraft part # awsf42c)). FYI If I interpret the info at motorcraft.com correctly, they started putting platinum plugs in stock in '93.
Opera House: Are you saying that, as long as the resistance measures out correctly (x ohms/foot I forget the exact number, but I've seen it in manuals and measured the resistance before on other sets, so it's just a matter of looking it up), you wouldn't bother replacing them?

 

[Opera House]

They only have two jobs to do

Conduct and insulate. Insulation is hard to inspect for. Most of the silicone jackets are pretty good and last a long time. When you see a wire arcing it is usually conducting along the skin from either end. I've opened hoods at night and seen little light shows. Cleaning fixes that right up. Have these alcohol wipes that work great. Usually avoid soaps unless it is in a dishwasher. Soap can leave a conductive film that will attract water. Incidently, I have the equipment that can HIPOT test to 60 KV but have never had to go to that extreme. Most resistance problems happen at the ends and I have recrimped ends a couple of times. One reason not to pull on the plug wires. Usually anything around 5K is ok. If you get internal arcing, the resistance skyrockets rather quickly.