TEST 1: Find The Dead Cylinder First
There are quite a few things that can fail on your 1.6L Honda Civic and cause a misfire or a rough idle condition, among those possibilities is a bad fuel injector.
The absolute best way to find out if the misfire or rough idle is being caused by a fuel injector... is to first identify the cylinder that's misfiring.
The fastest and easiest way to find the ‘dead’ cylinder is by doing a manual cylinder balance test and in this test section I'm gonna' show you how to do one.
Once you have identified the cylinder that's ‘dead’ (misfiring), it's gonna' be a hundred times easier to confirm if the misfire is really being caused by a bad or clogged fuel injector.
OK, this is what you need to do:
Remove all the metal retainer clips from all 4 fuel injector connectors (if applicable)
Depending on how old your 1.6L Honda Civic is, it may or may not have metal retainer clips on the fuel injector connectors. If your specific Civic doesn't have them, don't worry. Go on to the next step.
NOTE: Once you've removed the metal clips... make sure all of the connectors are connected to their fuel injectors before you start the next test.
Start the engine and let it idle,
Let the engine run for about a minute or two just to let the idle stabilize (even if the engine idle is rough).
Unplug the connector from fuel injector #1, while you observe the engine's idle.
What you're looking for, is to see if unplugging the connector (from the injector) makes the engine idle worse.
If the engine's idle DOES NOT get worse, when you unplug the injector's connector, then you've found a ‘dead’ cylinder. If the idle does get worse... the cylinder is active (not ‘dead’).
Repeat step 3 on the remaining 3 fuel injectors. Once you've found the misfiring cylinder or cylinders, take a look at the test result interpretations below.
CASE 1: You found a ‘dead’ (misfiring) cylinder. The next step is now to find out if the cylinder is misfiring due to a fried fuel injector.
This means checking the internal resistance of the injector, that belongs to the dead cylinder, with your multimeter. Go to: TEST 2: Measuring The Fuel Injector's Resistance.
CASE 2: You DID NOT find a ‘dead’ (misfiring) cylinder, repeat the test one more time.
If you still don't find a ‘dead’ cylinder with the manual cylinder balance test, then the rough idle condition that your Honda is experiencing is due a malfunction that's affecting all cylinders equally.
TEST 2: Measuring The Fuel Injector's Resistance
If you've reached this point, it's because you've found which cylinder is the one that's ‘dead’ (misfiring).
The next step is to check the internal resistance of the fuel injector that belongs to the ‘dead’ cylinder and then compare that resistance value to the other 3 fuel injectors.
NOTE: To get an accurate test result, your Honda's engine should be warm. If your 1.6L Civic doesn't start, don't worry about the warm engine part.
Alright, here are the steps:
Disconnect all four fuel injector electrical connectors from the fuel injectors. You may only need to test just one fuel injector, but I suggest you test them all.
Set the multimeter in Ohms mode and with the multimeter test leads, probe the first fuel injector's metal male spade terminals. Make sure that the multimeter test leads don't touch.
Write down the fuel injector's resistance your multimeter registers. You'll be using this resistance value to compare it to the other three in a few moments.
You should also write down to what engine cylinder the fuel injector belongs to. You can use the image in the photo viewer as an aid in identifying the cylinders.
The average fuel injector resistance value will be about 5 to 7 Ohms. Don't worry if these resistance values don't match the value of each of the four fuel injectors on your Honda Civic (you'll see why below).
Alright, with the resistance values of all six fuel injectors on paper, let's interpret your results. Choose from one of the following CASES:
CASE 1: All of the multimeter resistance values are nearly identical. This means that the fuel injectors on your Honda Civic are OK. The cause of the rough idle condition or a misfire condition or misfire codes, is not due to fried fuel injectors.
Here's why: When you do find one bad fuel injector, this one will register a totally different Ohms (resistance) value. And this will confirm beyond any doubt that that fuel injector is bad. So although this article doesn't give you a specific fuel injector resistance value for your 1.6L Honda Civic the fact that you tested them all and they are all registering the same resistance value, confirms the fuel injectors are not fried internally.
Your next step is to see if maybe the fuel injector is clogged. For this test, go to: TEST 3: Swapping The Fuel Injector.
CASE 2: One of the four multimeter resistance values is drastically different: this tells you that that particular fuel injector, on your Honda, with the drastically different resistance value is bad.
I suggest that you retest that fuel injector one more time to make sure of the Ohms (resistance) value. If this value is still the same as before, the fuel injector is bad.