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OT Spark plug wires

J

John-MI

Member
Is it really nessesary to change the plug wires on the newer cars that you change the plugs at 100,000 miles. Dealer seems to think so. Your opinions please. Thanks
 
Sometimes the wires or boots are brittle and crack when handled and cause a misfire.

The 'puter will QUICKLY inform you of that with a flashing MIL light and trouble codes.

If you change the plugs and there's NO misfire WHAT good are new wires going to do 'cept help with the dealership's bottom line?
 
The original plug wires were removed from my Nissan PU after 12 years and 120K and were put on the tractor temporarily until I could get a real set. That was 3 years ago. No problems yet. Two new cars have coil on plug. Aaron
 
Good suggestion. I've had four Ford vehicles suffer plug wire problems around 100,000 miles. One so bad I had a tough time getting home.
 
Ask your dealer why? Electricity follows the path of least resistance. If the spark it getting to the plugs, and not leaving the wires beforehand, and resistance reads correct, it's not going to cause you trouble.

I have many cars with over 200K and none have ever had wires.

Do they ever need replacing? Sure. But some outlast the cars they are in.

If no spark is leaving the wires prematurely, and they check out good with a resistance test - then buying new ones is throwing your money away.
 
Different approaches to a potential problem. I see a $100 set of wires as cheap insurance that I will not then have a problem, just as changing the timing belt at 90,000-100,000 miles. At $100/hour labor cost, would I rather pay someone to occasionally check resistance or just change them and be good for another 100,000 miles. If a person is willing to check them himself, obviously not an issue. But for me rather than screw around and check resistance on old wires and later need to recheck at some interval, I'll just replace them.
 
Some cars, particularly Generous Motors with coil packs, can damage the coil pack when plug wires go bad. Sometimes it can be cheap insurance to change the wires. Without knowing more particulars it is hard to say.
Hope this helps,
 
Timing belt has a pre-engineered useful/safe lifespan. Spark plug wires do not.

If a timing belt breaks - many new engines will self-destruct, with valves hitting the pistons.

If a spark plug wire starts to leak, the damage potential is next to nothing.

To each his own. I wouldn't pay anybody $100 an hour for work I can do myself. I also would rather pay $3 for a VOM and test my own wires - rather then pay someone to check for me.
 
A resistiance wire rarely goes completely bad, no continuity, all-of-a-sudden unless it gets physically damaged by something or somebody.
A wire developing high resistance over time, along with insulation leakage, is apt to cause weak igntion, leak off to ground, and a "check engine light" long before a coil pack burns itself off.
 
FOLLOW WHAT YOUR ONWERS MANAUL SAYS.

our 1999 Dodge van was right on the money at 30,000 plugs and 60,000 wires.

Engine would start to miss and I'd check when I did it last and sure enough that much time had went by and they were ready again.

I saw many times when I worked at the GM parts dept. where days or weeks after the 100,000 plug change a customers car would be back in for a missfire and it was the wire. Disturbing them can damage them. But not all the time.
 
Yes, I've had many plug wires that were fine until I had to change plugs and horse off stuck boots. Especially if a hemi-type engine with long boots that pass through the cam-train area.

That being said, not counting physical damage like that, I've had very few problems. Since modern engines use sophisticated electronics that can sense even small misfires or uneven firing/combustion - seems it makes sense to use that benefit and replace something when it is actually needed.

On the subject of Dodges, my 98 Grandcarvan with the 3.8 V6 got it's first plug change at 140K miles. I bought it from the original owner who just paid $200 for a "complete tune up and service." Yet, the original plugs were still in there burn-gapped at over a 1/4". And, even at that, that plug wires held up fine.

I see now why they use platiumum 100K plugs in those things. What an absolutely horrible job it is to change some of those back plugs. I can see why the service-shop cheated and did not change them during their expensive "tune up."
 
SURE, replace them ifffffffffffffff bad buttttttttt how do you know that???? If they arent routed incorrect where theres too much heat,,,,,, or they get kinked or pinched,,,,,,,,,,OR NOT DAMAGED BY REMOVAL OFF OLD PLUGS !!!!!!!!,,,,,,,,they may be fine. If you have her good n dark n watch you may be able to see breakdown problems.

That being said, if youre doing a 100,000 mile plug change I cant see how A NEW SET WOULD HURT PROVIDED THEYRE INSTALLED PROPERLY and its the type of thing I might just do while at Im at it.

I guess you can try just the plugs and if she checks out fine then youre money ahead...

John T
 
another thing i can tell you is that if they change your plugs and then next week you get a miss you will most likely go back and complain. then they will probably eat the repair, so they recommend it to cover their selfs. now if you refuse then it"s on you.
 
Been a while but if wires aren't better than they used to be, you would be lucky to get them off without damage after 100K miles. Some people don't remember the grease on terminals and plugs.
 
Not necessarily. OBD-1 won't set miss fire codes. Here is another instance for changing plug wires. We had an '02 Sebring in the shop today with a 3.0 Mitsu engine. We had to remove the plenum to repair a leaking valve cover gasket on the back side. With 115,000 miles on the odo, customer said to check and replace plugs and wires as necessary. My point in all of this is that different cars and circumstances demand different answers. There isn't just one answer to this question.
 
The poster asked if they "had to" be changed, not if wires EVER need changing.

And yeah, some cars have OBI instead of OBII, and some have no on-board diagnositics at all. In fact, some care don't even have plug wires. For older rigs, I doubt there's much that's going to get hurt by a bad plug wire.

I never said that plug wires never need to be replaced. But, to change them just for the heck of it at X amount of miles is a waste of time and money. I'll add, to compare changing plug wires - to changing camshaft belts - as somebody did here - is rediculous. Cam belts have strict mile-change requirements and can ruin an engine if they slip or break. Many new engines are still "interference" design.

If wires still have good insulation, good internal resistance, and boots - why on earth would somebody change them? No gain, no added reliability insurance, just money spent. In fact, I know that sometimes new aftermarket wires are inferior to the OEM wires that get removed.
 
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