I recently purchased a 1987 GT and noticed something unusual: At idle, I can see arcing between the metal spark plug shields and the head! I don't know how old the wires are, but they look almost new.
I repositioned the shields (pulled them slightly away from the head) and the arcing stopped. (Who knows what the front ones are doing, they're kind of buried in there.)
Is this arcing normal, or should I go buy some new spark plug wires?
Try applying a liberal coat of dielectric grease to the spark plug boots, see what your results are. I actually removed the shields from my V-6, that's your call though. On the firewall side, you can use a trouble mirror, after dark, see what's happening back there. The spark plug wires may be "el-cheapo", you know, just to sell the car.
The big question is what condition the firewall side plugs are in, as you may know, most folks tend to ignore them since thay're so hard to get at, you can pull a plug wire and get a visual on them, trouble mirror, get an idea of what you're up against.
Did you coat the inside of the boot (and the porcelin on the plug) with dielectric grease? Do you have the paper shields inside the metal heat shields? Are the heat shields pulled up on the boot (away from the tip of the boot) as far as possible?
the last couple of years, I've found you need to CHECK every wire with an OHM meter right out of the box. I bought 2 sets of autolite plug wires and both times found 2 wires were bad, Brand new ! you cannot take for granted because something is new that it is actually any good.
Having this same problem. Searched and found this thread. Did you ever find a solution? Mine has new plugs, cap, rotor, wires. Still arcing.
Years ago I wondered about this myself when I got my first V6 Fiero, and I read in these forums that this is... normal.
Keep in mind that I'm not talking about faulty plug wires that are actually shorting to ground. Arcing from the metal shields to the heads is caused by electrical induction. (I hope I'm using the correct term.) The arcing you see is not the same spark that is going to your plugs (but it's caused by that same charge).
[This message has been edited by Patrick (edited 10-04-2014).]
Hey thanks for the replies. I did use dialectric grease on the boot, but not on the plug...other than what transferred from the boot. My shields do have the paper inside and I do have them pulled as far up as possible. The wires are STI brand.
I wrapped a small amount of electrical tape around the end of the shield and that seems to have stopped it. But I doubt that with the heat, the tape is going to last. Bugs me because, from what ittle I understand about electricity... I'm assuming that if the spark is leaking out of the boot, that I'm not getting full energy at the plug.
But if it's normal, why didn't my old wires do it?
I'm just guessing, but perhaps the resistance was higher in your old wires, and this resulted in less electrical induction taking place.
The point is, the arcing you see jumping from the metal shields to the heads is not the voltage from the coil which is heading for the plugs. If it was, NONE of the voltage would be reaching the plugs, and none of those cylinders would be firing. Electricity takes the path of least resistance. The arcing is a by-product of the voltage going through the wires and metal shields in transit to the plugs.
I suspect that this arcing is a whole lot more common than most people realize. I didn't notice it until I looked at my engine running in pitch black darkness. I was pretty surprised at what I saw (and alarmed!), but found out eventually that it was nothing to worry about.
[This message has been edited by Patrick (edited 10-07-2014).]
I always pull the sheilds and toss them. I have yet to see a melted boot from running without the sheilds.
Some wires just suck, well most of them really. The cheap ones from autozone WILL leak spark right out of the box brand new. I go for the low ohm wires, sooo much better than the resistance core wires, and without any radio noise. Low ohm wires rarely will leak spark. IE less than 200ohms a foot, compared to 6,000 to 8,000 ohms per foot. Taylor makes some good wires. The only reason they made the wires so high ohms is to suppress radio noise, Jacobs came out with the design for the low ohms and zero radio noise, win win.
