Plug wires... Premature failure.

[JDWX]

97 Yukon 5.7 4x4 150k

I seem to go through a set of wires on a yearly basis...

Have used OEM Delco GM, and MSD wires once, I use the OEM Delco Cap and Rotor as well.

I've never had a vehicle eat wires like this (I have a Mustang with a serious coil and the fomoco wires are 5-6 years old and fine) . Last couple times I've replaced them, I used the diagram in Alldata for "properly" running them to reduce misfire. but, after about a year, I start getting misfire and codes due to misfire.

Is this typical? Or, might there be something causing this that I'm missing.

Thanks much for any thoughts on this!

 

[41racing]

Never had a problem like this before. You're definitely using quality wires though. Did you check for corrosion in the cap/rotor, and on the wire ends. You might want to try using some dielectric grease on the plug wire ends.

 

[79powerwagon]

My brother-in-law was eating caps and rotors on his late 90's Silverado for some reason. He finally threw a rod on the engine, and installed a new crate engine with a new distributor, and hasn't had the problem since.

You sure it's the wires?

 

[JDWX]

Never had a problem like this before. You're definitely using quality wires though. Did you check for corrosion in the cap/rotor, and on the wire ends. You might want to try using some dielectric grease on the plug wire ends.

That's what I thought as well. Every plug change, I've replaced cap and rotor with OEM Delco for good measure and always use small bit of die electric on every connection.

I'm baffled as to how they go south so fast... But once they start arcing, they just get worse and worse. to where at at 2200-2500 under stress the truck won't even pull more RPM and starts throwing misfire codes.

 

[JDWX]

My brother-in-law was eating caps and rotors on his late 90's Silverado for some reason. He finally threw a rod on the engine, and installed a new crate engine with a new distributor, and hasn't had the problem since.

You sure it's the wires?

At first I thought maybe a poppet or whatever.

But, pretty sure it's the wires, I can visually see them arcing to each other or to ground... Try my best to keep them isolated, but that's not exactly totally possible.

When I replace the wires, the issue goes away for a year and slowly comes back.

I just wonder if the AC/Delco wires I get from my auto parts store are the same quality I would get from a dealer.

Nonetheless, the MSD wires I used, did about the same. And I've had outstanding luck with those wires on my Mustangs.

The only odd thing about the setup, is that someone had stripped one of the distributor bolts, and I have to use a nut and bolt on it to secure it properly.

Thank you for your input guys.

 

[NYrr496]

Are you using all of the factory wire looms? You don't want them moving around and rubbing on anything.
I have 225,000 miles on my truck and I THINK I'm only on my third set of wires. After the factory set, I've used Bosch.

 

[corvhoe7795]

Maybe try a new coil or a good used one.

 

[41racing]

The coil is fine if it has enough power to arc through the wire to ground. You don't have some type of fluid leaking on the wires, do you?

 

[corvhoe7795]

This is the 3rd time I'm trying to answer you. I keep getting signed out for some odd reason. Maybe it's the high winds we been having messing with the cable.

 

[corvhoe7795]

Okay, that last one went.

Your wires are heating up from the inside out, too much voltage. Your wires are on the new side and your problem isn't from the wires arcing through the insualtion. That only happens when the insulation around the wires becomes old and brittle with hair line cracks. There's a lot of maybes to your problem, like the pick-up coil and ignition module inside the distributor. Maybe it's the coil mounted on the intake manifold too. I'd suggest going to the parts store and buying the Haynes repair manual. It explains everything in there on what could be the culprit with your problem.

As for wires my dad changed his last summer, the original ones had 118,000 miles on them. He's from the old school with his old cars. He shortened his new wires and put them over the top of the valve covers, like old cars used to be. He didn't want the hassles of putting them in the original looms. His wires look neat and easy to get to now if need be.

 

[JDWX]

The coil is fine if it has enough power to arc through the wire to ground. You don't have some type of fluid leaking on the wires, do you?

No, the engine bay is extremely clean.

 

[JDWX]

Okay, that last one went.

Your wires are heating up from the inside out, too much voltage. Your wires are on the new side and your problem isn't from the wires arcing through the insualtion. That only happens when the insulation around the wires becomes old and brittle with hair line cracks. There's a lot of maybes to your problem, like the pick-up coil and ignition module inside the distributor. Maybe it's the coil mounted on the intake manifold too. I'd suggest going to the parts store and buying the Haynes repair manual. It explains everything in there on what could be the culprit with your problem.

As for wires my dad changed his last summer, the original ones had 118,000 miles on them. He's from the old school with his old cars. He shortened his new wires and put them over the top of the valve covers, like old cars used to be. He didn't want the hassles of putting them in the original looms. His wires look neat and easy to get to now if need be.

Thank you for the input. I'm an reformed transmission diagnostics guy, and have Alldata. And I'm just stumped.

Everything is ran appropriately with the Alldata updated wiring diagram that is supposed to help preveny misfire.

I'm using factory looms and now even extra looms to help keep the wires away from each other and the block.

I replace the wires, they are fine for a year or so... I'm assuminmg they are breaking down somewhat and misfiring. ugh... And they are definitely misfiring through the wires, visual confirmation of arcing in the dark, and it's worse on wet days.

Not sure how it could be producing "too" much voltage. It's just the original OEM coil.


Thanks again for any input, I appreciate it.

 

[corvhoe7795]

This might sound crazy and dumb, but what about the alternator, is it putting out too much voltage. That kinda don't make sense as light bulbs would burn out and other wires might melt. My dad told me a story about some guy he used to work with. His cars volt gauge was showing 17 volts. But he forgets what the results of these 17 volts were. He does remember the problem wasn't blown light bulbs or even fuses. The guy bought a new alternator and his 17 volts on the gauge were gone. He thinks the guys problem was misfires, but he's not sure as this was like 30 years ago.