COP COIL TEST 2: Testing The COP Coil Without A Spark Tester
This test step is your starting point if you're testing for a bad COP coil without a spark tester.
The most important thing that you have to ascertain first, is which cylinders are the ones that are misfiring. By doing this, you'll know which COP coil or coils to test. If you haven't done so already, read the section: I Have Misfire Codes or I Have No Misfire Codes.
Once you have identified which COP coil you need to test, this is what you need to do:
- 1
Connect a vacuum gauge to any vacuum hose or line that has constant vacuum at idle. Now, start the engine and let it idle for a few seconds (for the idle to stabilize).
- 2
Now, disconnect the fuel injector's connector (of the cylinder the misfire code has identified as misfiring) and notice if the RPM's drop and if the vacuum gauge's needle reacts.
- 3
Repeat step 2 several times to make sure of your test result.
If the COP coil is truly causing or part of the misfire problem, you will not notice any changes in the hum of the engine (in other words, no RPM drop) and the vacuum gauge (if you're using one) will not register any changes in vacuum. - 4
Now, just for comparison purposes, disconnect the adjacent fuel injector.
Since the cylinder that this fuel injector belongs to, is not misfiring, you should feel a definite drop in the RPMs and the vacuum gauge will react to this drop. If this does happen, you now know that the COP coil that belongs to this cylinder is good. - 5
OK, once you have ascertained that the adjacent cylinder is working (not misfiring), turn off the engine and remove this COP coil.
- 6
The next step is to swap this good COP coil with the one that belongs to the misfiring cylinder.
- 7
Once both have been swapped (and are bolted in place), start the engine and repeat steps 1 thru' 3.
What you're looking for is for the misfire to move places and start affecting the cylinder that did not have one at the beginning of this test.
OK, let's take a look at what your test results mean:
CASE 1: If the misfire moved. This tells you that you do have a bonafide bad Coil-On-Plug (COP) ignition coil. Replace the COP coil.
CASE 2: If the misfire DID NOT move. This test result lets you know that the cause of the misfire is not due to a bad COP coil.
A misfire code and/or misfire condition can be caused by different things, like: bad fuel injector, low compression (in that specific cylinder, bad intake manifold gaskets, etc. For more info on this, look at the section: Other Misfire Causes and I also suggest reading the following article: How To Diagnose Misfire Codes P0300-P0308 (Ford 4.6L, 5.4L).
Other Misfire Causes
Unfortunately, nothing is ‘cut and dried’ when testing a misfire condition on the 4.6L and 5.4L Ford engines since so many things beside a bad COP coil can cause a misfire. In this section, I'll explore some of them.
There are 4 different photos in the image viewer that'll illustrate some of the most common causes of misfires.
Alright, here are some of the most common issues I have run across myself over the years:
- 1
Oil or antifreeze leaking into the spark plug well (tube).
In photo 1 You can see what a spark plug and coil boot look like when antifreeze is leaking on them. This is usually due to the intake manifold gasket leaking anti-freeze. Also, if the engine was washed, you'll get the same result.
In photo 2 You can see what a spark plug and coil boot looks like when oil is leaking on them. This is usually due to valve cover gasket problems. - 2
Carbon tracks on the spark plug boot and on the spark plug.
In photo 3 You can see what a carbon track on a COP coil boot and on a spark plug looks like.
If carbon tracks are found, they can not be cleaned/ scraped off. The coil, coil boot and spark plug have to be replaced.
- 3
The Coil-On-Plug's electrical connector is broken. More specifically, what breaks is the locking tab that prevents the connector from becoming disconnected from the COP coil. This is a very, very common problem on the 4.6L and 5.4L Ford engines. If you do have some of these connectors that are broken, you can buy them here: PICO 5713PT FORD Ignition Coil-2
- 4
The fuel injector's electrical connector is broken. More specifically, what breaks is the locking tab of the fuel injector connector. Road vibration and the like will eventually make the connector come disconnected and will cause an intermittent connection or no connection at all. This is another very, very common problem on the 4.6L and 5.4L Ford engines. If you have broken fuel injector connectors, you can purchase them here: PICO 5714PT FORD Fuel Injectors.
The key to finding out what's causing the misfire condition or misfire codes (if the COP coil is working and sparking), is to inspect the coil boot, the spark plug or spark plugs, the fuel injector and COP coil electrical connectors.
If the COP coil is sparking (as confirmed by COP COIL TEST 1 and 2) then you can look into testing the compression of that particular cylinder and testing the fuel injector.
You can find the links to the 4.6L, 5.4L fuel injector test and compression test in this section: More Ford 4.6L, 5.4L Test Articles.
