Changing spark plugs

[Ah GetFd]

Yes, a faulty coil pack can absolutely cause the ceramic insulator on a spark plug to crack, along with causing electrode erosion, heavy fouling, or melting due to overheating and misfiring. A malfunctioning coil can produce excessive voltage (over-voltage stress) or cause extreme thermal stress, which damages the plug.

Fair enough.

A coil is just a lump of wire.

The more turns there are the more voltage you can develop when you collapse a magnetic field across it. And you can control it by the number of turns of wire you put in it. You can't generate more voltage than the number of turns of copper are there.

What can happen however if a coil is not working properly is that the spark plug wont work at all. The spark plug can then foul up. A spark plug may crack if there is excessive heat generated in the cylinder. Thats a possibility.

I am just stating a fact. Its not "high voltage" cracking a spark plug. They are designed for high voltage.

As AI will tell you.............spark plugs fouling, closing the gap, shorting to frame, short out coils....not the other way around.

So if your coil pack fails it is most likely the spark plug caused it. Change both

 

[Ah GetFd]

Well now. Ignorant "unwashed" masses remain ignorant when the experts argue/debate what the heck is going on. Heh!

At least I can go take a bath.

 

[Snicklefritz]

So if your coil pack fails it is most likely the spark plug caused it. Change both

Yes, and if the coil is now bad, it will kill each spark plug that you put in, quickly. That is what I described. So, why did we have this back and forth?

 

[Ah GetFd]

Yes, and if the coil is now bad, it will kill each spark plug that you put in, quickly. That is what I described. So, why did we have this back and forth?

No. The coil can't do anything. It can't kill spark plugs. All that can happen with a dead coil is that the spark plug won't work

 

[Ah GetFd]

Yes, and if the coil is now bad, it will kill each spark plug that you put in, quickly. That is what I described. So, why did we have this back and forth?

You are changing both because the spark plug is faulty and it has taken out the coil not the other way round. Once you short the spark plug it no longer has the resistance it should with the air gap so you short the coil. The coil fails along with the plug......

 

[Snicklefritz]

No. The coil can't do anything. It can't kill spark plugs. All that can happen with a dead coil is that the spark plug won't work

Lookee, we are in a semantics argument. Dead coil results in another dead plug. Because in order to function the plug must have a functioning coil. So, a dead coil does cause spark plug failure by not "being there" for the plug. My replacement plugs were burned and cracked. BECAUSE the coil was bad. It kept causing plugs to crack. Two of them cracked and burned two weeks after installation. THEN the coil was replaced. I had to tell them to look at the coils. They were just pulling the plug and sticking another one in and saying "all better now".

It's not proven - can't be after the fact of an additional 4K miles - that the coil was gone yet. Do they fail over time? So, the second plug failure may have been still on a partially functioning coil. Or, as you assert, the moron/shop flunky broke two plugs in a row and that finally killed coil - or killed it earlier. But if so, it wasn't all at once, because my growing misfire issue didn't turn into a CEL one until near the end of those 4K miles. You tell me. How long can it take to kill a coil?

 

[Ah GetFd]

A coil is just a lump of wire

It can't do MORE than it is supposed to......

It's job is to supply spark plugs with a high voltage. The spark plug is designed for that. That's why it's made of porcelain to insulate the terminal and centre electrode from the frame.

If you were to short the centre electrode directly to the frame then eventually, and a coil of wire is pretty resilient, the coil would fail. The air resistance between the centre electrode and the frame electrode of the spark plugis no longer there and a larger current will flow rather than a "spark" jumping a gap of thousands of ohms which is why you needed a high voltage in the first place.

When you connect the centre electrode to frame bypassing the air gap you have created "no resistance" by grounding the centre electrode to the frame. So a larger current will flow and probably destroy the coil.

And the most likely event is that the spark plug is cracked and has gone to frame or the electrode has become fouled over time, carbon built up, the electrodes became closer together, even shorted then destroyed the coil.

Now you can argue that the coil cracked the spark plug......but how?

It might be that for some reason the coil was not made properly, so insulation inside had broken down, or it was dropped, but most electrical products have to survive a drop test during manufacture.

The coil was somehow damaged internally which then would cause a spark plug to not spark properly, foul up, the cylinder overheated, the spark plug got damaged through heat. Thats a scenario.

But in normal operation, we are not talking about spark plugs not being made properly and coils not being made properly we are talking about normal operation.

And the operation you would expect (because you have to change spark plugs) is that they degrade, that the electrodes become "closer" through carbon build up, there is excessive heat, the spark plug has cracked through heat or damaged when it was installed. The coil however is a lump of wire. It's not expected to be an item that is replaced regulalrly like spark plugs.

I have had "coils" fail on GM engines. It might be manufacture, but I think it far more likely that it was a spark plug well overdue for replacement that caused it.

In previous cars I have owned for 20 years since new. I have never had a coil failure.