I looked at a maintenance schedule and site search and did not see when the spark plug wires should be replaced. I am replacing the plugs now at 100k miles. Should I replace the wires too or are they supposed to last longer.

 

It would be a good idea.

 

well i was talking to my grandfather who has been a mech. his whole life and he says that wires should not need to be replaced unless there was damage done to them. i too thought i should replace my 3.4L wires but he said unless they are damaged you should not need to. so it saves me $70.

 

You can test the wires to see if they are in spec. I think you just need a multimeter for that

Belize: I think it depends on what brand of wires you use for your application. Like say with our yotas, if we use OEM or (maybe) NGK, they will probably run for lifetime, but if we use other off brands, I'm sure they are not designed to last 300K+ miles, and are more easily damaged--heat, voltage, etc.

 

Very true. Toyota wires should last the life of the vehicle assuming there is no damage.

 

When in doubt check the FSM to test the cables for resistance and inspect for any physical damage or electrical arcing.

 

Good advice guys.

 

like jessekosten said, checking the resistance against what the service manual says is the best way to know the condition of the cables!

 

My original stock looked pretty good at 125k but I replaced them anyways while I did the plugs. It is really easy to do and the new NGK's were really high quality. I don't think they have to be done, but it is for peace of mind. One little crack and you could be left stranded sometime.

 

Wires are relatively cheap, might as well change them out with the plugs every 60K or 90K. $29 for NGK wires on Amazon with free shipping.

How necessary??? Hard to say, my 22RE still has the original wires after 210K, but that will soon change now that I'm no longer going to the dealership for maintanence.

 

replace the plugs/wires with OEM. just did it on mine and it made a noticable difference

 

Not all damaged spark plug wires are visibly damaged. I had spark plug wires that were causing misfires, but I absolutely could not see any issues. I even replaced the plugs because I saw no damage or burning or anything on any of the plug wires. Replaced the plug wires and the misfire went away.

 

I'm nearly at 200K should I be doing my coil packs next time I do my plugs ?

 

you only need to replace them if you have a miss or a studdering engine under acceleration. i just replaced mine because of this. fixed the problem

 

my 91 needed a replacement at 200k, and they def had been replaced before that. my 87 they have been replaced and need replacement at 160k. I noticed they dry out, and the boots get a bit brittle. concern of arcing and failure causes me to change them out everytime i do a tune up...they are not that expensive so i find it worth it.

 

i only changed mine because when i changed plugs they came apart when pulling them out.

 

changed mine recently and my 4runner runs better. the wires where 9 years old when changed. on my OEM plugs, toyota printed the year the plugs where manufactored right on them.

 

even thou i'm not an expert, here is just some simple common sense.

first, how do you determine if the wire is damaged?
you can test with a meter to know if the current resistance is up to spec, big cracks are easy to detect, but the wire isolation is under extreme heat during a long period of time, rubber/plastic(or what ever) will dry and crack, some of the micro cracks can cause micro arcs happen during ignition while the human eyes can not see, a simple meter can't tell the difference either.

second, i bought complete set of plugs and wires include tax for $56, all OEM from Northridge Toyota, last year. 3.4V6 has coil packs, only needs 3 spark plug wires that's why it's cheap. i didn't saving a bit by skipping it, for the next 100k miles.