Troubleshooting primary/secondary ignition problems

[GrantM]

My 2003 Explorer 4.6L is running rough. Code keeps coming up p0358 which is the primary and secondary ignition failure for cylinder 8. Have changed the COP with no improvement or clearing of code. Have looked at a tutorial to troubleshoot this problem but need some clarification on just what to do:

The idea is to check whether the PCM is sending a pulsed signal to the COP. When I remove the plug from the COP, looking at it with the locking clip facing downward there are two female terminals: the left one goes to a green striped wire and the right one to a red striped wire.

My questions are when using a voltmeter in Hertz mode,
1)Which of the two terminals on the plug(red or green wire) do I place the probe from the voltmeter to check for the pulsed signal?

2)Where do I place the other probe from the voltmeter - do I need to place it at all, or does it go to ground, or does it go to the other terminal on the plug?

Thanks

 

[2000StreetRod]

COP voltages

Battery voltage is applied to COP primary via the WHT/LT BLU wire when the ignition switch is in Run or Start.

The PCM "grounds" the other coil primary lead (WHT/RED wire) to build an electromagnetic field (EMF) in the coil. When it is time to ignite cylinder 8 the PCM "opens" the connection to "ground" causing the coil EMF to collapse inducing a voltage in the secondary winding that connects to the spark plug.

If the COP connector is removed and you insert your meter probes in the two female pins you should read battery voltage with the meter set to DC and the ignition switch on but the engine not running. With the starter motor cranking the engine you may see the voltage drop from battery to zero for an instant but I doubt it if you're using a digital voltmeter because it only samples the voltage reading periodically. Even a test light may not flicker because the filament stays hot longer than the duration of the ignition pulse. But reading battery voltage between the two female connector pins at least indicates that the wiring is good to the COP connector.

 

[shucker1]

An old analog voltmeter like a Simpson 260 may work?

Your best bet would be an oscilloscope to catch a pulse that fast.

 

[GrantM]

Thanks for the explanation. So I will place the voltmeter probes in each of the female plug terminals simultaneously. I think the AC current setting on the voltmeter that measures frequency should then have a reading at the plug if the PCM and the wiring is intact.

 

[shucker1]

It may or may not. I've never tried.
I would think not because you actually never cross absolute zero to create a sine wave.
The internal trigger and counter in the Fluke may not pick it up as a cycle.

Interesting theory though.

Your best bet is to buy a tool called a Noid Light. It's specifically designed for what your trying to do.