How To Test The Ignition Coils (2003-2006 2.4L Honda Accord)

TEST 3: Swap The ‘No Spark’ COP Coil

You've reached this point because you've got a COP ignition coil that is not sparking. The next step, is to swap this coil with another and I don't mean going out and buying one. I mean simply swapping this ignition coil with another one that's already on your Honda's engine.

The idea behind this ignition coil swap is twofold:

• We're gonna see if the non-sparking coil will now spark when connected to another electrical connector.
• -AND-
• See if the other ignition coil (that is sparking) will spark in the non-sparking coil's electrical connector.

Why this extra step? This is just to make sure that the non-sparking ignition coil is getting all the 3 signals it needs to spark (these 3 signals are: power, ground, and the triggering signal).

Alright, this is what you'll need to do:

1. 1

   Disconnect and remove the COP ignition coil that did not spark.

2. 2

   Choose one of the other COP coils that is sparking and remove it from its place.
   
   If you need to make sure that this COP ignition coil is sparking, you can test it with your spark tester.

3. 3

   Once the good COP coil is removed, connect it to the bad COP coil's electrical connector.

4. 4

   Next, connect the HEI spark tester to the good COP coil.

5. 5

   Ground the HEI spark tester with a jump start cable directly on the battery negative (-) terminal.

6. 6

   Place the bad COP ignition coil in the location of the good one you just removed and bolt it down.

7. 7

   Once everything is ready, have your helper crank the engine.

8. 8

   The good COP coil should spark.
   
   This would confirm that the 3 signals are present in the COP coil connector.

Let's take a look at your test results:

CASE 1: The COP ignition coil sparked. This tells you that the COP coil that did not spark in TEST 2 is bad and needs to be replaced.

Here's why: By placing a good and sparking ignition coil in place of the bad one and having spark come out of the good one, then this proves that:

• It's getting power (10 to 12 Volts).
• It's getting the PCM's Triggering signal (known as the IC (Ignition Control) Signal).
• It's being fed with Ground.

CASE 2: The COP ignition coil DID NOT spark. This tells you that the reason why the COP coil did not spark is because it's lacking one of the 3 signals it needs to spark.

The next step for you is to:

• Check that the ignition coil is being fed with power (10 to 12 Volts).
• That the PCM's is providing Triggering signal (known as the IC (Ignition Control) Signal).
• That the ignition coil is being fed Ground.

Although these specific tests are beyond the scope of this article, you now have an idea of what direction your diagnostic/troubleshooting needs to go in.

TEST 4: How To Do A Cylinder Balance Test

Having a rough idle or misfire condition that doesn't set a misfire diagnostic trouble code (P0301, P0302, P0303, P0304) is pretty common. This can make it difficult to pinpoint the problem.

Thankfully, there's a simple solution and it involves doing a cylinder balance test to find out which one is the ‘dead’ cylinder. The cylinder balance test simply involves disconnecting one fuel injector at a time (while the engine is running) to see which one doesn't have an effect on the engine's idle when unplugged.

If this is happening in your particular situation, this is what you'll need to do.

1. Start the engine and let it idle.
2. Disconnect one fuel injector at a time.
   • What you're looking out for is the fuel injector that DOES NOT make the engine's idle worse (when you unplug it from its connector). If this happens, then this cylinder is the ‘dead’ one.
   • In a good cylinder (one that's contributing to engine power), when you unplug the fuel injector from its connector, the engine's idle will get worse (it'll be very noticeable!).
3. Once you've tested all of the cylinders in this way, write down the cylinder's number who's unplugged injector did not make the idle worse.

Let's take a look at what your cylinder balance test results mean:

CASE 1: Unplugging a fuel injector had NO EFFECT on the engine's idle. This test result tells you that that particular cylinder is ‘dead’

You can now start from TEST 2 and check to see if the COP ignition coil is bad or not.

CASE 2: Unplugging all of the fuel injectors (one at a time) had an effect on the engine's idle. This tells you that all of the ignition coils and fuel injectors are working as they should.

If you're still experiencing a rough idle condition then more likely than not, one of the following problems applies to your Honda:

1. One or more engine cylinders have very low compression or the individual compression of the cylinders varies more than 15%.
2. Vacuum leak from leaking intake manifold gaskets or vacuum hoses.
3. Dirty fuel injectors.

Although testing the above conditions is beyond the scope of this article, you now know in what direction you need to take your troubleshooting.