A bad or clogged fuel injector can cause a rough idle or a misfire that will severely decrease your 1.5L Honda Civic's engine performance.
The cool thing is that testing for a bad fuel injector (or a clogged one), on your 1.5L Honda Civic DX, isn't hard. In this tutorial, I'll explain how to check for a bad fuel injector by doing a simple multimeter resistance test.
I'm also gonna' offer you a specific diagnostic guide to finding the bad (or clogged) fuel injector in case you don't know where to start your troubleshooting efforts (in page 2 of this tutorial).
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar los Inyectores de Combustible (1992-1995 1.5L Civic) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
Having worked on cars for a good part of my life, I can tell you that most fuel injector problems fall into one of two categories. Simply put, the fuel injector stops injecting fuel completely or gets clogged and doesn't inject enough fuel.
When a fuel injector stops injecting fuel completely, it's usually due to the fact that it's internal coil winding has suffered some failure (like a short or an open). Testing this type of failure is simple and involves doing a multimeter resistance test (and this is the focus of TEST 1).
But before I get ahead of myself, let me tell you about the most common symptoms you'll see when a fuel injector fails:
- Rough idle.
- Lack of power.
- Hesitation when you accelerate your 1.5L Honda Civic down the road.
- Misfire trouble codes (OBD II equipped only):
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
The focus of this tutorial is to see if the fuel injector's internal coil has failed (and thus causing the fuel injector to stop injecting fuel) but testing for a clogged injector isn't that much more complicated and I'll show you how in the next page.
Checking The Injector's Internal Resistance
As mentioned at the beginning of this tutorial, we're gonna' test the fuel injectors' internal coil winding. If a fuel injector's internal coil winding is fried (either because it's shorted or is open), its resistance value will not coincide with the factory resistance specification. This spec is 10 to 13 Ohms (Ω).
The test steps below assume that you're testing all four fuel injectors. Alright, let's get started:
Disconnect the fuel injectors from their harness connectors.
NOTE: To identify which cylinder the fuel injector belongs to, see the above illustration with the cylinder # id for the 1.5L Honda Civic.
Set your multimeter to Ohms (Ω) mode and:
Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads.
Write down the resistance value that your multimeter records for the specific fuel injector you're testing. The illustration above will help you identify the cylinder # the fuel injector belongs to.
Repeat steps 1 through 3 on the remaining fuel injectors.
NOTE: The 1.5L Honda Civic resistance specification is: 10 to 13 Ohms.
Let's find out what your specific multimeter test results mean:
CASE 1: The fuel injector resistance of all 4 was within specification (or similar). This confirms that the fuel injectors are OK. Specifically, that none are shorted or open internally.
Here's why: If any one of the fuel injectors were shorted or open internally, the fuel injector would have registered a radically different resistance value on your multimeter. Since the resistance values for a 4 were uniform, this test result tells you that they are not defective.
Your next step is to go to the next page and see the troubleshooting guide here: How To Find The Bad Or Clogged Fuel Injector.
CASE 2: One of the fuel injectors registered a completely different resistance value. This indicates that the fuel injector is bad. Replace the fuel injector.