This article will help you to diagnose a misfire condition lighting up the check engine light on your 4.6L or 5.4L Ford vehicle with the following misfire diagnostic trouble codes: P0301, P0302, P0303, P0304, P0305, P0306, P0308.
More specifically, this article is designed to help you troubleshoot a BAD Coil-on-Plug (COP) ignition coil with step-by-step testing instructions.
Alright, to help you navigate this article a little easier, here are its contents at a quick glance:
IMPORTANT: Before you start, read the following first:
TIP 1: The very first thing you have to do, before you start testing with the info in this article, is to find out which cylinder or cylinders are misfiring. Please read the following sections: I Have a Misfire Code(s) or I Have NO Misfire Code(s) before jumping into COP COIL TEST 1.
TIP 2: Most of the testing, that you'll be doing, is done with the engine cranking... so be careful and stay alert. My biggest suggestion to you is to have your helper wait outside the vehicle as you set up the test to avoid having him or her crank the engine accidentally.
TIP 3: You'll notice that the photos and the testing instructions call for an HEI spark tester. If you don't have one, you can use any other type of spark tester (although the results may not be as accurate). If you want to know why I recommend the HEI spark tester, go to section: Why the HEI Spark Tester.
There are several ways to find out if the COP ignition coil on your Ford 4.6L or 5.4L is BAD or not. One is using a spark tester and is the most accurate way of testing for a BAD Coil-on-Plug (COP) ignition coil. The other is without one and requires that you swap the some COP coils to find out. I'm gonna' explain both in this article.
Now, you don't have to read the entire article to use the info presented here but, I suggest you do. To help you effectively use this test article, read the following CASES and follow the one that applies to your specific testing situation/ needs.
DIAGNOSTIC TEST OPTION 1: You have a spark tester and plan to troubleshoot the COP coils with it, start at COP COIL TEST 1.
DIAGNOSTIC TEST OPTION 2: You don't have a spark tester, start here: COP COIL TEST 2.
The first thing you need to do, is to see if the COP coil is sparking and this test step will help you with this.
You'll notice that the photos and the testing instructions call for an HEI spark tester. If you don't have one, you can use any other type of spark tester (although the results may not be as accurate). If you want to know why I recommend the HEI spark tester, go to section: Why the HEI Spark Tester.
The following testing instructions assume that you already have a specific cylinder in mind to test:
Remove the Coil-on-Plug (COP) coil that you need to test.
It'll be necessary to disconnect the COP coil from its electrical connector to remove it. The locking tab on the connector breaks very easily... so be careful unplugging it from the coil.
Using a battery jump start cable, ground the HEI spark tester to the battery negative (-) terminal.
Now, have your helper crank the car (or pick up or van) as you watch the HEI spark tester (from a safe distance).
The HEI spark tester will give you one of two possible results: spark or no spark.
If you're testing multiple cylinders, repeat steps 1 thru' 4 on the other COP coil that the misfire code has identified as misfiring.
OK, let's take a look at what your test results mean:
CASE 1: You got spark: this means that the cause of the misfire code and misfire condition is not due to a lack of spark. You can also deduce, from this result, that the ignition coil pack and the spark plug wires are OK.
I suggest that you check to see that the 1.) spark plug and the spark plug boot do not have carbon tracks. 2) That the spark plug does not have its porcelain insulator cracked. 3.) That antifreeze isn't leaking into the spark plug well. For more info (and photos) on these possible conditions, see section: Other Misfire Causes.
CASE 2: You got no spark: this test result usually means that the COP coil is fried, but not always. I suggest that you verify that the COP coil is getting power and its switching signal before you replace it.
Here's why: The COP coil that you just tested (and that didn't spark) receives power in the form of 12 Volts DC and a switching signal that comes directly from the PCM (Powertrain Control Module= Fuel Injection Computer). If any of these two are missing, the COP coil won't spark and you just might replace something that will not solve the misfire problem/issue.
How can you check for power and the switching signal? This can easily be done by simply substituting another COP coil (that is sparking and that is not setting a misfire code) and checking if this one sparks with your spark tester. If this one sparks, then you know beyond a shadow of a doubt that the COP coil is getting both power and the switching signal, therefore it's BAD and needs to be replaced.
“I never made a mistake in my life. I thought I did once, but I was wrong.”
Charles M. Schulz