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

TEST 1: Checking For Misfire Codes

The very first thing you need to do, check for misfire codes. More likely than not, if your Honda is experiencing a bonafide misfire condition, the check engine light (CEL) is shining nice and bright on your instrument cluster and this means that there's a diagnostic trouble code (DTC) stored in the computer's memory.

Why check for diagnostic trouble codes first? Because the misfire code will help you in identifying which cylinder is the one that could have a bad ignition coil and knowing which ignition coil to test is half the misfire diagnostic battle.

Now, if you don't have a scan tool, you can still use the info in this tutorial but you'll need to do a cylinder balance test. For more info on this, go to: TEST 4: How To Do A Cylinder Balance Test.

Let's get started:

1. 1

   Connect your scan tool or code reader to the diagnostic link connector (DLC).

2. 2

   Turn the key to the ON position.

3. 3

   Read the diagnostic trouble codes stored in the computer's memory.

Choose from one of the cases below:

CASE 1: You have a misfire code. The next step is to find out if this misfire code is being caused by a bad COP ignition coil. Go to: TEST 2: Check The Ignition Coil For Spark.

CASE 2: You have a P0300 misfire code. This means that whatever is causing the misfire condition, is affecting all of the engine cylinders and not just one.

This code, the (P0300) usually rules out a bad COP ignition coil and/or a fuel injector as the culprit. Although it's beyond the scope of this article, I do have a few suggestions for you and these are to:

1. Check to see if one or more engine cylinders have low engine compression.
2. Check for vacuum leaks.

CASE 3: You DO NOT have any misfire codes. This usually means that the rough idle that your Honda is experiencing is not being caused by a bad COP coil.

Now, the keyword here is ‘usually’ because your Honda could have a bad COP coil. What I suggest you do, is to do a cylinder balance test (TEST 4: How To Do A Cylinder Balance Test).

Also, and preferably after you do the cylinder balance test, you need to do a thorough visual inspection of the spark plugs, COP coils to see if:

• Spark plugs are not:
  • Soaked in engine oil (leaking valve cover gasket).
  • Soaked in water (from power washing the engine).
  • Cracked or broken.
  • Center electrode's gap is filled/covered with carbon (from the cylinder burning oil).
• COP coils are not:
  • Soaked in engine oil (leaking valve cover gasket).
  • Soaked in water (from power washing the engine).
  • Cracked or broken.

If all of the above checks out, I would suggest an engine compression test.

TEST 2: Check The Ignition Coil For Spark

After having identified the misfiring cylinder (either through a diagnostic trouble code check or a cylinder balance test), the next step is to check to see if the COP ignition coil is sparking or not with a spark tester.

My instructions below call for an HEI spark tester and if you don't have one, you may be wondering if you can use any other type of spark tester.

And the answer is: ‘Yes, you can use any type of spark tester you want or have’. The only reason I use and recommend the HEI spark tester is because this spark tester is accurate (and you don't have to worry about interpreting the color of the spark).

OK, to get this pie baked, this is what you need to do:

1. 1

   Remove the ignition coil from its place on the valve cover.

2. 2

   Connect an HEI spark tester to the ignition coil.

3. 3

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

4. 4

   When everything is set up, have a helper crank the engine while you observe the spark tester.

5. 5

   The spark tester will do one of two things: Spark or not spark.

Let's see what your test results mean:

CASE 1: The COP ignition coil sparked. This is the correct and expected test result and tells you that the ignition coil is OK.

Now, since that cylinder is the one that the trouble code is accusing of as being ‘dead’, you now need to look to see if and/or perform the following tests:

• Check to see if engine oil is dripping onto the spark plug and COP coil boot from the valve cover gasket.
• Check to see if the spark plugs have carbon tracks on their porcelain insulator.
• Do an engine compression test to see if that cylinder has low engine compression.

CASE 2: The ignition coil DID NOT spark. This test result usually means that the COP ignition coil is bad but there's one more thing that you need to do (to make sure that the COP coil is truly bad).

The next step is to simply swap that ignition coil (that didn't spark) with another and then check both coils for spark. For this test and a better explanation of ti, go to: TEST 3: Swap The ‘No Spark’ COP Coil.