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Exactly how does a bad sparkplug wire, or a bad boot, blow out the ceramic insulator of a plug ? The spark travels from the coil to the top of the plug. If the plug isn't bad, as in new, how does the insulator break ? I just can't quite picture this in my mind. My new wires seem to have, for now at least, stopped my plug breakage problem. But the dealer said there was no way an engine can break an insulator, and I buy that, since I can't imagine how it would happen. So for the sake of my sanity, does anyone know how this works ? There have been others in here with broken insulators, so it's not a real uncommon problem. Thanks y'all.
Ken, 99 Silver Frost SE Zetec Atx, polished alloys, Kumho's, Pioneer hi power CD/AM/FM. Factory spoiler (added) Audi side lites, Borla stainless steel muff. Stolen, recovered in pieces. Looking for another Tour, preferably V6, 5 speed.
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I immediately had that same question & here is how it was explained to me. If the plug wire or coil is going bad, it causes a mis-fire. The ECU then kicks up the voltage to the suspect cylinder to try & force spark through the plug & avoid damage to the engine. As the voltage spikes, this raises heat within the plug causing the core to expand & burst the insulator.
So, you can have good plugs in the engine, but if the wires or coil create too much resistance, the ECU still must raise the voltage to get adequate spark to that plug and poof, the plugs burst from the excess heat that is generated from an over-voltage condition.
Great to hear your car is running well. I hope it continues & serves you for a long time to come.
JimR
Must be that jumbly-wumbly thing happening again.
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That all makes sense to me.
Most people I spoke to had never heard of spark plug ceramics breaking. They all figured that I must have broke them either installing them or taking them out..... NOPE!
We'll see how mine look in a few weeks when I pull them out to look at them.
It sure is running good except for the vibration in the steering wheel when it idles. It has done this from about 60K on.
Danny Brown
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Never heard of this one either - but anything's possible!
Are you using the correct plugs?
Have you dropped any othe plugs or could they have been otherwise damaged?
Can the plugs be defective?
You may want to contact the plug manufacturer to get their opinion. I did this several years ago with Bosch and they sent me a nice, detailed letter.
Dan B.
96 SE 2.5 auto
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The coil pack is not capable of generating enough power (current x volts) to overheat and break an insulator. In order to generate heat from the tip of the insulator to the electrode (through the center of the insulator) you would have to have considerable current and some resistance. Since the center electrode is very low in resistance and the spark current is very week thereā??s just no heat, not to mention that the spark duration is so short that all the heat would be quickly dissipated. All the heat comes from the combustion chamber.
Cracked insulators are cause by a poor casting, miss handling during shipping or installation, excessive shock and vibration and excessive compression.
jeff
have you fixed your ford lately?
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Originally posted by TourDeForce:
I immediately had that same question & here is how it was explained to me. If the plug wire or coil is going bad, it causes a mis-fire. The ECU then kicks up the voltage to the suspect cylinder to try & force spark through the plug & avoid damage to the engine.
As the voltage spikes, this raises heat within the plug causing the core to expand & burst the insulator.
So, you can have good plugs in the engine, but if the wires or coil create too much resistance, the ECU still must raise the voltage to get adequate spark to that plug and poof, the plugs burst from the excess heat that is generated from an over-voltage condition.
No offence, but where are you getting this stuff?
The coil voltage is not adjustable. Peak spark voltage available depends upon coil winding ratio. If dwell (coil saturation) is not sufficient, output voltage is reduced. Final spark voltage reached depends upon spark plug gap, the compressed mixture's dielectric value, or leakage which drains energy causing a spark somewhere besides the plug's tip. Ignition module and wiring problems can reduce spark voltage. So can shorted secondary windings on the coil. Increased plug wire resistance reduces spark current. The spark only contains a few watts of power. This will not blow anything up.
As most books will tell you, shattered plug insulators are usually caused by detonation. Crossfire between leaky plug wires can cause occasional detonation. Detonation causes drastically increased pressures within the cylinder and can damage plug tips and ceramic insulators.
"Those who cannot remember the past are condemned to repeat it" -George Santayana
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Originally posted by dbbubba:
That all makes sense to me.
Most people I spoke to had never heard of spark plug ceramics breaking. They all figured that I must have broke them either installing them or taking them out..... NOPE!
We'll see how mine look in a few weeks when I pull them out to look at them.
It sure is running good except for the vibration in the steering wheel when it idles. It has done this from about 60K on.
Danny Brown
Everyone I talked to had never heard of this problem, with the exception of a few of you here. This problem is somehow related to the plug wires. I think it's the boots that went bad from me pulling them out to R&R the plugs the first time. I think I cracked them when I pulled them off the plugs, and somehow the spark is shorting out to the head through the middle of the plug instead of arcing across the gap. Therefore the broken insulators. But it's that part of it that I don't understand, it seems like there would be alot more resistance to go through the insulator and out to the head than to just continue on to the tip and across the gap. But I got the same questions from almost everyone, "are you sure you didn't break them yourself" ? "Did you drop them ? Did you overtighten them ? Did the plugs flop around inside the plug wrench" ?
Ken, 99 Silver Frost SE Zetec Atx, polished alloys, Kumho's, Pioneer hi power CD/AM/FM. Factory spoiler (added) Audi side lites, Borla stainless steel muff. Stolen, recovered in pieces. Looking for another Tour, preferably V6, 5 speed.
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I got this info from an engineer who supposedly worked for Champion. I'm beginning to have my doubts about his qualifications based on the post you just put up. Maybe this is why he doesn't work for them any more? (if he ever really did - I got to talk to him on the phone & although he seemed mostly competent, he did strike me as a bit elusive in his response to certain questions - I don't know him personally). I did not research further to verify his information since he was supposedly well versed in this field, & DB & Ken needed answers ASAP.
I'm just happy that the miss problems that DB & Ken were having seem to be resolved, but time will tell for sure. Interestingly, the suggested solution for both scenarios turns out to be the same - change the plug wires along with a new set of plugs.
Thanks for your informative post by the way. I am always open to additional info since I am a back yard mechanic and no expert on cars. I also appreciate your gentle delivery! I'll take time to verify second hand info before I post in the future, or at least qualify it and/or add a disclaimer. 
Ken & DB, I apologize for leading you down this road when I had no clear view myself. Things seem to be working out well thus far, so we are lucky there. I will double check my sources in the future.
Last edited by TourDeForce; 09/12/03 05:11 PM.
Must be that jumbly-wumbly thing happening again.
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It just occurred to me that this guy works for Florida Power & Light, my supplier of electricity. Perhaps I should worry! 
Must be that jumbly-wumbly thing happening again.
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No apologies required!
Any info was quite welcome to me! My problem was largely due to the faulty/failing coilpack. Replacing the plugs and wires was a cheap solution in my hunt for the problem. As a consiquence I got to experience the cracked plugs and the fact that only AZFS-22PP will work in th Zetec!
When I get time I am going to gap the plugs at spec.
Danny Brown
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