What Tests Can I Perform To Find The Cause Of The Misfire Condition?
Thankfully, there is a logical step-by-step process to diagnosing the root cause of a cylinder misfire. The following testing suggestions are the ones that I've used over many years with good success.
STEP 1: Identify the dead cylinder. If your 1995 Honda Civic is OBD II equipped, this is usually means reading the misfire diagnostic trouble codes with a scan tool. Then by matching the misfire code to its engine cylinder using an illustration of the engine cylinders.
If your Civic is not OBD II equipped, you'll need to do a manual cylinder balance test by unplugging one fuel injector at a time (to see which one has NO effect on the engine's idle).
- The following tutorial will explain in-depth how to do a manual cylinder balance test (if you Honda has multi-port fuel injection):
Once you've found the ‘dead’ cylinder, the next step is to check for spark.
STEP 2: Check for spark . 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:
- Perform a spark test (using a dedicated spark tester) on the spark plug wire of the ‘dead’ cylinder..
- 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.
- Check to see if the ‘dead’ cylinder's spark plug boot and spark plug are swimming in engine oil from a leaking valve cover gasket.
- If the ‘dead’ cylinder is getting spark (as confirmed by your spark test), the next step is to remove the spark plug and check them for wear and tear, carbon tracks, anti-freeze, etc.
- If the spark plug wire does NOT spark, then there's a good chance the spark plug wire or the distributor cap is bad.
- These components can be tested and you can find the tests here:
- How To Test The Igniter, Ignition Coil Accord, Civic, CRV, and Odyssey (at: easyautodiagnotics.com).
- Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnotics.com).
If all your tests indicate that spark is reaching the ‘dead’ cylinder and all of the ignition system components (spark plug, spark plug wire, distributor cap, etc,) are OK, then the next step is checking that cylinder's fuel injector.
STEP 3: Test the fuel injector. If the ignition system is not the cause of the misfire, then the next step is to check the ‘dead’ cylinder's fuel injector (this section applies to the multi-port fuel injected Civics).
You'll need to:
- Do a resistance test on the fuel injector to make sure it's internal coil does not have a short-circuit or an open-circuit.
- Do a Noid light test on the fuel injector's connector to make sure your Civic's fuel injection computer is activating it.
- You can find the fuel injector resistance test here:
If after making sure that the fuel injector's internal resistance matches the other 3 and that the fuel injection computer is activating it... the next step is checking the ‘dead’ cylinder's compression.
STEP 4: Test the compression of the cylinder. After eliminating the ignition system and the fuel system as the sources of the misfire, we now need to make sure that the ‘dead’ cylinder is compressing the air that's entering it.
You'll need to:
- Check all 4 cylinders with a compression tester. You need to test all 4 to find out if the ‘dead’ cylinder's compression value is within an acceptable range of the highest compression value obtained from testing all 4 cylinders.
- Check for vacuum leaks.
- You can find the engine compression test here: How To Test Engine Compression (Honda 1.5L).
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 A Misfire?
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 1.5L or 1.6L Honda car.
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:
- Ignition System Tests:
- Spark tester.
- Test light.
- Fuel System Tests:
- Noid light.
- Fuel pressure gauge.
- Engine Mechanical Tests:
- Compression tester.
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.