How To Test a Misfire Condition and Misfire Codes (Honda 3.0L)

What Tests Can I Perform To Find The Cause Of The Misfire Condition?

In the previous page we discussed that the misfiring cylinder will misfire (or go ‘dead’) due to a lack of fuel, or spark or air, so you might be asking yourself, ‘What do I start testing first?’.

Well, if I where in your shoes and I was the one troubleshooting the misfire, I'd start by first finding the ‘dead’ cylinder and then making sure that it was getting spark.

The following diagnostic strategy should help you find and resolve the root cause of the misfire or ‘dead’ cylinder on your 3.0L Honda:

STEP 1: Identify the dead cylinder. Since your Honda Accord is OBD II equipped, this can usually be done by reading the misfire diagnostic trouble codes stored in the car's fuel injection computer with a scan tool. Then by matching the misfire code to its engine cylinder using an illustration of the engine cylinders.

In many cases, the PCM does not give you any misfire codes, even though the engine is suffering a bonafide misfire. In these cases and if your Honda Accord has multi-port fuel injection (one injector per cylinder), you'll need to do a manual cylinder balance test by unplugging one fuel injector or one COP ignition coil at a time (to see which one has NO effect on the engine's idle when unplugged from it's electrical connector).

The fuel injector or COP ignition coil that does not worsen the engine's idle when unplugged tells you that that specific cylinder is ‘dead’.

STEP 2: Test the ignition system . Since the majority of misfires are caused by a failed component in the ignition system, it's important to make sure that the misfiring cylinder is getting spark. You should:

Distributor Type Ignition System:

1. Perform a spark test (using a dedicated spark tester) on the spark plug wire of the cylinder that the misfire code is accusing of being dead.
   • Testing for spark with a spark tester is the most important first test since you'll know right away if the misfire is due to a lack of spark.
2. Check to see if the spark plug boots and spark plugs are swimming in engine oil from a leaking valve cover gasket.
3. If you got spark from your spark tester (from the cylinder the misfire code is accusing of misfiring), the next step is to remove the spark plug or spark plugs (of the affected cylinders) and check them for wear and tear, carbon tracks, anti-freeze, etc.
4. If you get no spark, then the next step is to check for spark directly on the distributor cap tower that feeds that spark plug wire. If you now get spark here, then the spark plug wire is bad and they all need to be replaced. If you get no spark, then the distributor cap is bad and you should replace it along with the distributor rotor.

Distributor-less Type Ignition System (COP ignition coil system):

1. Test the COP ignition coil with a spark tester to see if it sparks or not.
2. Check to see if the spark plug boots and spark plugs are swimming in engine oil from a leaking valve cover gasket.
3. The following tutorials will help you:
   • How To Test The Coil on Plug Ignition Coil (Honda 3.0L) (at: easyautodiagnotics.com).
   • Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnotics.com).

STEP 3: Test the fuel injectors. If the ignition system is not the cause of the misfire, then the next step is to check the fuel injectors.

You'll need to:

1. Resistance test each of the 6 fuel injectors.
2. Do a Noid light test of each one to make sure the PCM is pulsing them (activating them).

STEP 4: Test the compression of each engine cylinder. Other tests that should be done, if the ignition system and fuel injectors check out OK are:

1. Engine compression test.
2. Checking for vacuum leaks.
3. You can find the engine compression test here: How To Test Engine Compression (Honda 3.0L).

The above list of steps may seem/sound like troubleshooting a misfire is a complicated thing but it really isn't. Depending on your level of ‘wrenching’ experience, this is something that you can accomplish without taking it to the shop.

What Tools Do I Need To Test The Misfire Code(s)?

Finding the exact cause of the misfire codes or misfire condition is possible with the proper tools. Without them, you won't be able to diagnose/troubleshoot those issues on your 3.0L Honda car or mini-van.

Depending on what the root cause of the misfire is, you may need several tools. Most of these you can buy online, none of these will break the bank and I'll make some recommendations on them. Here's a guide to some of the basic tools that can be and are used:

1. Ignition System Tests:
   • Spark tester.
   • Multimeter.
   • 12 Volt test light.
2. Fuel System Tests:
   • Noid light.
   • Fuel pressure gauge.
   • Multimeter.
3. Engine Mechanical Tests:
   • Compression tester.

Now of course, you'll also need basic hand tools like: screw-drivers, ratchet wrenches, sockets, etc. You'll also need a generic scan tool to retrieve the diagnostic trouble codes (DTCs) from the computer's memory (if OBD II equipped).

Keep in mind that using the right tool for the job will save you time, frustration, and /or keep you from damaging the component that you're testing.

More 3.0L Honda Accord And Odyssey Tutorials

You'll find a complete list of Honda 3.0L tutorials in the following index: Honda 3.0L Index Of Articles.

Here's a small sample of the articles/tutorials you'll find in the index:

• How To Test The Starter Motor (Honda 3.0L).
• How To Test Engine Compression (Honda 3.0L).
• How To Test The Coil on Plug Ignition Coil (Honda 3.0L) (at: easyautodiagnostics.com).
• The Basics Of Crank And Cam Sensors And How To Test Them (at: easyautodiagnostics.com).

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