Quite a few things can cause a misfire in one or several cylinders. For example: bad spark plugs, a bad distributor cap, bad spark plug wires, low engine compression in one or more cylinders, bad fuel injector, etc.
I could go on and on, listing more possible 'bad' components but you get the idea. The good news is that with a good diagnostic strategy (of tests) you can find out exactly what's wrong yourself.
In this tutorial, I'm going to explain in some detail the most common causes of misfires and more importantly, I'm also gonna' offer you a simple diagnostic strategy that I'm certain will help you 'nail down' the cause of the misfire condition or rough idle condition your Honda is experiencing.
Contents of this tutorial:
ES 
You can find this tutorial in Spanish here: Cómo Probar Una Falla En Cilindro (1.5L Honda) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 1.5L Honda Civic: 1992, 1993, 1994, 1995.
- 1.5L Honda Civic Del Sol: 1993, 1994, 1995.
What Is A Misfire Condition?
Every cylinder, in your 1.5L Honda Civic's 4 cylinder engine needs air (compression), fuel, and spark to produce power.
It's when one of these 3 things is missing from a cylinder that that cylinder will misfire. This misfire will cause a rough idle condition and/or a misfire on acceleration.
Here are a few other symptoms you'll see when your 1.5L Honda Civic is misfiring:
- If OBD II equipped, the Check Engine Light will be on with one or more of the following misfire codes:
- P0300 Random Cylinder Misfire.
- P0301 Cylinder #1 Misfire.
- P0302 Cylinder #2 Misfire.
- P0303 Cylinder #3 Misfire.
- P0304 Cylinder #4 Misfire.
- Lack of power upon acceleration.
- Smell of unburned gas exiting the tail pipe.
- Rough idle and may stall.
- Cranks but does not start.
- Will not pass the emissions tests.
- Bad gas mileage.
Although the misfire codes don't tell you what exactly is the cause of the misfire or rough idle condition, there is a way to find out exactly what is causing it.
One of the most important things you need to know, to successfully diagnose a misfire or rough idle condition, is what causes a misfire. Let's go to the next subheading and find out.
What Causes A Misfire Condition?
Keeping in mind that each cylinder in your 1.5L Honda Civic's engine needs spark, fuel, and air (compression), we can start looking at the specific systems that are tasked with providing them.
Ignition System: The ignition system is tasked with creating and delivering spark to each of the 4 cylinders. The ignition system is usually the culprit behind most misfires.
The usual suspects (that cause a misfire) are:
- Bad spark plugs.
- Carbon tracks on the spark plug and spark plug boot.
- Bad distributor cap.
- Oil dripping (from the valve cover) onto the spark plugs and spark plug boots.
Fuel System: The fuel system is responsible for making sure that fuel reaches each cylinder. Fuel system components that can cause a cylinder misfire, when they fail, are:
- Bad fuel injectors (multi-port fuel-injected Civics).
- Broken fuel injector connector (this is a very, very common problem).
- Electrical short in the fuel injector wires that are keeping the fuel injector pulse signal from reaching the fuel injector.
- This is usually the result of human error and after a major mechanical repair where the wiring harness was damaged.
- Bad fuel injection computer not pulsing the fuel injector (this is a very rare condition, but it happens).
- Bad fuel pump.
Engine Mechanical Condition: The pistons and cylinder head valves are the ones that draw air into the engine and compress it. Usually all cylinders wear out evenly but every now and then, either thru' lack of maintenance or some mechanical problem, you'll have one or more wear out at an accelerated pace.
To make the long story short, those cylinders (with accelerated wear and tear) produce a less than average compression value that will cause a misfire condition.
Other issues, that can not be overlooked are vacuum leaks.
With this info under our belts, let's turn the page and find out what to test.
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 that the "dead" cylinder is getting 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.
- 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.
STEP 3: Check the "dead" cylinder's spark plug and spark plug wire boot.
- 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.
- We also need to check and see if the spark plug boot and spark plug are swimming in engine oil from a leaking valve cover gasket.
- 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: easyautodiagnostics.com).
- The following case study is a classic example of how oil leaking onto a spark plug can cause carbon tracks to develop (on the spark plug) and cause a cylinder misfire:
- Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.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 4: 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 5: 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 (1992-1995 1.5L Honda Civic).
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.
- Multimeter.
- Test light.
- Fuel System Tests:
- Noid light.
- Fuel pressure gauge.
- Multimeter.
- 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.
More 1.5L Honda Civic Tutorials
You can find all of the 1.5L Honda Civic diagnostic tutorials in this index:
Here's a sample of the tutorials you'll find in the index:
- How To Test The MAP Sensor (1992-1995 1.5L Honda Civic).
- How To Test The Fuel Injectors (1992-1995 1.5L Honda Civic).
- How To Test The Throttle Position Sensor (1992-1995 1.5L Honda Civic).
- How To Test The Alternator (1992-1995 1.5L Honda Civic).
If this info saved the day, buy me a beer!
