TEST 3: Swapping The Fuel Injector
There are cases in which the fuel injector isn't fried internally and so it passes TEST 2 with flying colors. Yet the fuel injector is the one causing the cylinder to misfire.
This usually happens when the fuel injector is clogged and its spray pattern isn't atomizing the fuel correctly.
The best way to find out if this is happening is to swap the fuel injector of the ‘dead’ cylinder with its neighbor on the fuel injector rail.
NOTE: This test works and makes sense doing only if you have identified the ‘dead’ cylinder and have done TEST 2: Measuring The Fuel Injector's Resistance.
IMPORTANT: Take all necessary safety precautions, since you'll be working around fuel in this test step. Gasoline is extremely flammable. Your safety is your responsibility. If you have never removed/replaced a fuel injector before... consult your Honda's repair manual (no, not the owner's manual in the glove box!).
This is what you'll need to do:
Remove the fuel injector , of the cylinder that you found to be ‘dead’ when you did the manual cylinder balance test in TEST 1.
IMPORTANT: Consult a service repair manual for detailed instructions on how to remove and replace a fuel injector.
Swap the fuel injector, with another. This other fuel injector has to come from a cylinder that you confirmed was not ‘dead’ in TEST 1.
Re-install the fuel injector rail as per instructions in a service repair manual.
Start the engine, after confirming you have no fuel leaks and that the fuel that spilled during the fuel injector swap has completely dried.
Perform the cylinder balance test per the instructions in TEST 1.
What you're looking for is to see if the misfire has now moved to the cylinder where you installed the fuel injector you suspect is bad.
CASE 1: The misfire moved to where the fuel injector was swapped: This test result tells you that the fuel injector is bad and needs to be replaced.
CASE 2: The misfire DID NOT move to where the fuel injector was swapped: If the misfire stayed put in the same cylinder (even after swapping the fuel injector), then you now know that the fuel injector is good.
Since the cylinder is still misfiring... you now need to check that the fuel injector is getting both power and its activation signal with a Noid light. The following tutorial will show you how to do a Noid light test:
- How To Do A Fuel Injector Noid Light Test (GM 3.8L) (although this tutorial is written with GM 3.8L equipped vehicles in mind.. the info applies to your Honda Civic).
NOTE: If your Noid light test confirms that the fuel injector is getting both power and the activation signal, then the next steps are to make sure that neither spark nor compression are missing in that cylinder. The following tutorials will help you:
- How To Test Engine Compression (1.6L Honda Civic).
- How To Test Misfire Codes (1.6L Honda Civic).
- How To Test The Accord, Civic and Odyssey Distributor Type Ignition System (at easyautodiagnostics.com).
Fuel Injector Troubleshooting Guide
If you think you have a bad fuel injector but aren't quite sure where to start, in this section I'm gonna' offer you my fuel injector troubleshooting procedure. The following guide will help you get to the bottom of the problem, whether it's caused by a bad fuel injector or something else.
OK, the most important thing you need to do is identify the ‘dead’ cylinder. Because if you do have a bad fuel injector on your hands, your Honda Civic will have a misfiring cylinder.
These are the steps I take:
- Check for Misfire Codes.
- Unfortunately, the PCM usually doesn't set a specific bad fuel injector code, but when a fuel injector does go bad, you WILL see a Misfire Code.
- The idea here is to find the ‘dead’ cylinder. Now, if you have no misfire codes and yet the engine in your Honda Civic is misfiring, then you need to do a manual cylinder balance test.
- A cylinder balance test involves disconnecting one fuel injector at a time, while the engine is running, to see which one (when disconnected) has NO EFFECT on the engine's idle. The one, when unplugged, that doesn't cause the engine's idle to get worse is the one that belongs to the ‘dead’ cylinder.
- The next step is to check for spark.
- It's very important to eliminate the ignition system as the root cause of the misfire or ‘dead’ cylinder.
- What I'm looking for here is that spark is actually reaching the spark plug. This is accomplished using a dedicated spark tester on the spark plug wire.
- The following tutorial will guide you step-by-step thru' the whole procedure: How To Test The Accord, Civic and Odyssey Distributor Type Ignition System (at: easyautodiagnostics.com).
- Next, I remove the spark plugs and visually inspect them.
- What I'm checking for are for cracks and/or carbon tracks and/or oil filling up the spark plug well.
- Honda 1.5L and 1.6L engines have a bad habit of leaking engine oil onto the spark plugs and spark plug wire boot and this is a common cause of an engine miss (Misfire).
- If everything above checks out OK, I then do an engine compression.
- This is a fast and easy test but is so often overlooked.
- You can find this test here: How To Test Engine Compression (1.6L Honda Civic).
- Check fuel injector resistance.
- I also do a fuel injector Noid light test to make sure that the fuel injector (that belongs to the ‘dead’ cylinder) is getting power and the activation signal from the fuel injection computer.
- Since the fuel injectors are pretty easy to get to, I have also swapped them out to see if the misfire condition moves to the fuel injectors new location (as checked by the manual cylinder balance test).
The purpose of all of the my tests (above) are to eliminate the ignition system and engine mechanical condition first before attempting to blame or suspect a bad fuel injector.
And I can tell you that this diagnostic strategy has saved me from replacing some good fuel injectors and being able to nail down the ones that are bad.
Related Test Articles
If you're trying to diagnose a misfire condition (on your Honda vehicle) and this test didn't help, I suggest taking a look at the articles in the 1.6L Index Of Articles.
If you need and/or want to test the Distributor Ignition System to see if it's the source of the misfire condition (or Misfire Code: P0300, P0301, P0302, P03030, P0304), you can go to this link: How To Test The Accord, Civic and Odyssey Distributor Type Ignition System (at easyautodiagnostics.com).
Here's a small sample of the tutorials you'll find in the index:
- How To Test Engine Compression (1.6L Honda Civic).
- How To Test The Starter Motor (Honda 1.5L, 1.6L).
- How To Test For A Blown Head Gasket (1.6L Honda Civic).
- How To Troubleshoot A No Start (1.6L Honda Civic).
If this info saved the day, buy me a beer!