Distributor-less ignition system coils?

ALEX STATHAS

MEMBER
2014 NISSAN VERSA
1.6L
4 CYL
2WD
AUTOMATIC
85,000 MILES

Hi, our vehicle listed above SV has a coil-on-plug direct distributor less ignition system with four individual ignition coils on each spark plug, those ignition coils sell for $125.00 each at Advance Auto Parts or $500.00 for all four of them before the repair shop marks them up to make a profit on them, my question is what happens when those direct distributor less ignition coils fail, do they all fail at the same time and cause a crank but no start condition which wears out the starter motor and the battery or do they fail one at a time which cause the engine to misfire or run poorly or run rough and does the misfiring engine coil leak raw unburned gasoline into the crankcase from the cylinder where it misfires from diluting the engine oil? Those four direct distributor less ignition coils connect to the spark plugs through spark plug boots, I know that spark plug wires in very long ago older cars with an ignition distributor I know that older spark plug wires were arcing but can the spark plug boots in recent coil-on-plug direct distributor less ignition systems can those spark plug boots arc and cause a reduced voltage of secondary ignition current from the direct distributor less ignition coils' secondary windings to the spark plug electrodes and how long do the direct coil-on-plug distributor less ignition system coils last before they begin misfiring or before they go out completely? Thank you in advance for your helpful and enlightening information. Written by Alex Stathas

1 Reply

AL514

MECHANIC
4,122 POSTS

Hello, these are known as smart coils because they have a turn on transistor inside of them, that's why they have 3 wires going to each coil. And yes, these coils can fail and spark out the side of the boot if there is high resistance through the spark plug or a fuel injector that is not fueling enough. Clogged fuel injectors can overwork an ignition coil causing premature failure. Your oil level should not be rising on its own under normal running conditions. Normal blow by past the piston rings will not cause the oil level to be high. A fuel injector over fueling, failing piston rings, weak ignition spark can cause over fueling of a cylinder therefore causing cylinder wash. These types of things can cause fuel to get into the oil. These coils usually fail one by one over time. Not all at once. I'll put up a diagram showing the internal working of the ignition coils. When replacing them, using aftermarket components is not the best idea, especially AutoZone, advanced auto, etc. You want coils that are going to last, so buying OEM coils might be more, but in the long run you'll save from premature failure. These coils also have a higher firing voltage so when testing spark be extra careful. If you're finding your oil diluted with fuel, doing a fuel injector balance test can help determine if they are all flowing the correct and same amount. Are you getting any fault codes for anything?
If you have a scan tool that can look at live engine data, you can check the Long and Short Term Fuel Trims. They will tell you if the engine computer is adding fuel to the air fuel mixture or reducing fuel from it.

The yellow wire going to the coils is the 12v feed wire, the black wire is a shared Ground. And you'll see an odd colored wire on each coil, for coil number 3 it's a brown wire, that wire is the control signal coming from the engine computer, it's a lower voltage square wave signal. Usually, 0-to-4-volt signal that turns on the base of the transistor, which in turn powers up the coil primary, when the transistor is turned off the primary winding causes a magnetic field to collapse and induces high secondary voltage which travels out to the spark plug.
This is what you would see for a turn on signal to the coils from the engine computer (ECM) if you're using an oscilloscope to check for an ECM output to them. The coils are designed like this to prevent damage to the ECM if a coil shorts out.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

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