If you've been wondering how to test the Coil-on-Plug ignition coils on your Ford car or truck (with a 4.6L or 5.4L V8) to see if one or several are BAD and are causing a misfire... this is the article for you.
As is the custom here at easyautodiagnostics.com, the tests steps are explained in detail and the diagnostic/troubleshooting is accomplished in several easy steps.
OK, before we jump into the COP coil tests, let me just make you aware where you can find a complete list of 4.6L and 5.4L ‘How To Test’ articles that are located in this Web Site and at troubleshootmyvehicle.com and this list is found here: Ford 4.6L, 5.4L Index of Articles.
One last thing... I have written another 4.6L, 5.4L COP coil article that is a little leaner than this one... you can take a look at it here: Ford 4.6L, 5.4L Coil-on-Plug Misfire Tests (this article is located at troubleshootmyvehicle.com).
This is not the most definitive list on the subject, but does cover the majority of symptoms I've seen on this type of ignition system:
A scan tool (atomotive diagnostic scanner) isn't needed to test the COP ignition coils on your Ford car or truck. The tests you're about to learn are all done without one. Now, what if you don't know which cylinder is the one misfiring? Don't you need a scan tool to find out? Well no, you can find out which one it is without a scan tool. You can perform the cylinder balance test yourself on your Ford car or truck, Test 5 will help you with this. You'll need:
OK, to test the Coil-on-Plug ignition coils on your Ford car or truck, you need to know what each wire (circuit) does in the connector. Here are the circuit descriptions:
You don't need to know the color of the wires for this test since the circuit descriptions (above) are shared by all of the eight Coil-on-Plug ignition coils on your Ford car or truck. So, whether you're testing the number 1 cylinder ignition coil or the number 4 cylinder ignition coil (or whichever ignition coil)... the above info applies.
To test these circuits, it's not necessary to unplug the ignition coil's connector. What I recommend you do is to test for each signal with the connector connected using a Wire-Piercing Probe. This is the easiest and the most effective way of getting at the signals. If you need to see what this tool looks like, click here: Wire-Piercing Probe.