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COP Diagnostics Part II: Those Pesky Ford Coils

Introduction

If you have been in the industry a while you probably know that Ford COP ignition coils are a common failure item. They can often be easy to pick out when they are misfiring, but what about when they are intermittent? Another potentially worse situation is a vehicle that leaves a shop after a coil has been replaced only to return in a couple of weeks with a different coil failing. Should the shop have replaced all 8 (or 10) coils? That is an option, albeit an expensive one. However, there is a way to determine coil health that can help a technician make that judgment call.

Finding the Cylinders Responsible

The first step in misfire analysis is identifying the bad cylinder or cylinders. This step can be done with a scan tool in most cases. The next step is to scrutinize additional test data so that we have confidence when we point at a particular fault. That is what diagnostics are all about, correct?

P03xx codes are usually a pretty good gauge of what cylinder is the problem. These codes may, or may not, be set due to ignition issues. Regardless, we still have to find the cylinder and the cause. For the sake of education let's tackle some misfires, explain the theory and learn some techniques.

This first place to look for a misfire on a Ford, especially a miss that doesn't set a code, is in the Mode$06 data. Rick Seagle wrote an article about Ford Mode$06 Misfire Data that does a great job outlining how to use this information effectively. Below is an example of a 1999 E150 with a 5.4 liter engine and a noticeable single misfire occasionally.

In this case the Mode$06 data shows that the PCM has counted a minute number of misfires on cylinder number 3. The misfire is definitely there, but it's failure rate is well below the threshold that would set a P0303 code. Now this doesn't mean we just throw a coil at cylinder number 3, but it does alert us as to which cylinder we might want to keep an eye on during further diagnosis.

This technique can also be used to draw our attention to potentially weak coils during other P03xx code diagnostics. This next example is of a 2000 E150 with a 4.6 liter engine and a P0302. We can see that cylinder number 2 is over the limit and fails the misfire monitor, hence the code and MIL command. We can also see that cylinders 1 and 7 also have some recorded misfires but remain below the code setting limit. Would these be good coils to keep an eye on during our diagnosis? Later in this article we will explore how to verify potentially weak ignition coils. In this case, coils 1 and 7 were in fact weak and were replaced along with coil number 2 to fix the vehicle properly and avoid a comeback.

A side note on Mode$06: it should be taken with a grain of salt. In theory it should work, but it doesn't always. It is a good tool to point us in the direction of which cylinders have misfired when it does work. When it does not work, however, we may end up back at diagnostic square one. To illustrate my point here is a Ford with a P0301 stored and the MIL commanded on. This Mode$06 data is worthless in regards to our misfire diagnosis on this particular vehicle.

Now that we have identified a misfiring cylinder(s) we need a method to test the ignition system to see if it is the cause of the misfire. Secondary ignition patterns can be tough on COP vehicles to say the least. Primary ignition patterns are relatively easy to obtain on most Ford vehicles with individual coils. D-Tip's Coil ...

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