I have an 03 G35, which is irrelevant to my post.

Recently a coil pack crapped out on me and got me wondering, why does just one coil go when they all get the exact same duty with equal amounts of run time.

But when I pulled the coil, I decided to take a look at the spark plug cause I just got the car and never checked out the plugs. And I found that the spark plug wasn't tight at all. It was screwed down finger tight.

Now, when I was younger I used RTV silicone to seal up a subwoofer box and in haste, I installed the sub and hooked it up. It sounded great. I made some noise for an hour or so and turned it off when I got to work. After my shift, I turn on the subwoofer and it smoked and put the amp in protection.

How are these two things related? Well, the fumes from the RTV dissolved the lacquer coating off the wires which create the subwoofers voice coil. I'm willing to bet that my dead coil was a direct result of that loose spark plug and the gasoline fumes pouring past the threads on every other stroke.

 

It could be, but it's also because of simply the way items fatigue. 6 coils, even manufactured at the same time, have tolerances. So it's rare that all items fail at the same time. However, it could also be looked as a leading indicator, meaning the first coil failed, how long behind are the others.

You just never know. I have a 28 year old car that has only had one coil fail, it was about 10 years ago, the others are fine. I have another 18 year old and once one failed, the rest were only a few months behind, and they all failed finally.

 

Yes a loose spark plug will kill a coil pack.

POWER is a measure of voltage X amperage, they are inversely proportional. As one goes up by X% the other does the opposite. By not having the spark plug tight you have created resistance in the circuit (lower voltage) that needs to be overcome by increased amperage.

Amperage means heat, this is why electrical wire is sized not by how many volts is present but by how many AMPS ARE DRAWN, your fuses are rated in AMPS.

Heat melts electronics, degrades thermoplastic insulation, and destroys stuff.

Hope this helps.

 

I think you win the thread. Not sure why my mind didn't go straight to the coil pack being overloaded due to the poor connection in the circuit. Here I was thinking the fumes caused the failure. Thank you sir.

I got another coil from a local junk yard and checked the plug underneath it before buying it.

 

I had to replace one COP..followed soon after by another two...
so I went in and did the last 3 once again.

6 cops replaced over 3 visits...

All plugs were new prior to the first cop failure.
All has been fine since all cops were replaced.

 

There is also a capacitor (they call it an ignition condenser) on the coil pack positive wire that may have failed which would help explain why you had so many coil packs die so fast.

It's this black electrical "box" on the right side of the motor, between the valve cover and the battery box.

 

Two failed months apart, but I got tired of replacing them a bit at a time. We bought one..then another one..then I begged her to let me do the remaining four as a preemptive strike.

I have also heard experienced folks say that they tend to go over time one by one.
There have been no problems 30-40k miles after..then one failed because I had torn the silicone cop boot during the install..dohhh.
Thanks, I will look into it though.

The audi was the same after 200k..after got the cop recall done at 140k miles.​​​

 

They typically die from overheating the winding and melting the coil. It's just a transformer that steps your 12vdc up to about 14Kvdc. In the electrical industry we would call 14k volts "medium voltage" and the coil pack has all the same multiple shielding layers that we also use for MV wire in the field. The insulation on the coil pack is protecting it from arcing out against grounded components nearby.

Here's where it gets tricky, the coil is closing the circuit UNDER LOAD, literally the moment the ECM shuts the ground (power is delivered full time to the coil on the G35, some vehicles it's the other way around) there is a massive surge of power flooding into the coil, this creates a sort of a "ripple" in the flow of current since it's happening so microscopically fast. These ripples cause your 12v nominal (it's actually 14.5vdc due to the alternator generating current) to fluctuate a little bit. The ignition condenser is there to mitigate this.

Imagine you have a 5 gallon bucket on your roof with a hose attached to the bottom of it and it's pouring rain outside, you can squeeze the spray nozzle just a tiny bit and a lot of pressure comes out. If you were to hold down the sprayer it would shoot out a lot of water for a few seconds then it quickly loses pressure because the bucket is going empty, you're losing head pressure, and the rain isn't falling fast enough to keep your bucket full. If you were to just squeeze the sprayer a tiny bit at a rate where the rain can keep the bucket full then you can continuously have a bunch of high pressure sprays. If you exceed that duty cycle then your spray would be a bunch of weak sprays as the bucket empties.

The ignition condenser (old European word for a capacitor that's still used for automotive terminology) is basically the bucket in that analogy. The alternator is the rain. The voltage is the water. The condenser holds enough power on that circuit that when the coil packs drain off voltage there's a big enough reservoir that there is no drop in voltage for the other coil packs.

If your ignition condenser is failing there isn't enough of a reservoir of power and the other coil packs will open when there is less than nominal voltage on the circuit, it takes time for electrons to move, sure it's INCREDIBLY fast but so is the ignition firing sequence when you're at higher rpms. If the coil is closing when your voltage is low it causes the amperage on the circuit to increase, amperage generates heat, heat melts the insulation on the coil windings. The spark plug WILL fire, even if voltage is lower, it just uses amperage to make up the difference, up to the point where something finally melts, either the coil pack or the fuse protecting the circuit.

The fuse doesn't necessarily protect the coil from a bad condenser though, The fuse is to protect the insulation on the wire FEEDING the coil pack from melting and causing a fire, the secondary side of the coil winding are these almost microscopic fine little wires and their insulation is substantially less than the power delivery circuit.

Other things can cause a coil to fail though, not having a spark plug properly torqued, corrosion on the threads of the spark plug (hence why I always recommend using aluminum anti-seize, it's as much for preventing corrosion as it is for not stripping threads when removing), poor engine to chassis ground, oil in the spark plug well tube causing the voltage to arc out directly to the valve cover instead of the controlled arc on the spark plug.

Ever have your windows in the house open and you go to close a door and it SLAMS SHUT with a fury that rocks the entire house? That's what's happening (electrically speaking) inside the coil if it's going directly to ground instead of having that air cushion to arc across. This is why when you're testing for spark you hold the ground strap a mm or two away from ground source or you hold the threads of the spark plug up to something metal instead.

When that magnetic field collapses violently it also generates a lot more heat since the electrons are literally being SUCKED towards the ground source (like that door slamming in the wind), normally the electrons need to be PUSHED across a gap to arc.

Fortunately ignition condensers are cheap, anytime someone has a coil pack failure I strongly recommend just replacing it with another one (it's like $10) as well as cleaning up the engine main bonding jumper and the negative battery wire (both ends of both wires).

 

Sounds like a charge packet dampner. Sorta like a injector fuel line dampner.

 

Yep, very similar to the concept behind fuel line dampers which smooths out the pulses from the fuel pump.

 

Or smooths out the opening and closing reflections of the injectors,
Like an electrical transmission line termination.