How To Test The Fuel Injectors (1.6L Toyota Corolla)

How To Find The Bad Or Clogged Fuel Injector

There's a simple and logical process to finding out if the misfire (engine miss, rough idle) on your 1.6L Toyota Corolla (1.6L Geo Prizm) is being caused by a clogged or bad fuel injector.

The diagnostic guide, below, has helped to accurately diagnose a failed/clogged fuel injector about 95% of the time and this has meant saving time, frustration, and $$$. The troubleshooting process below will also help you!

OK, below are the diagnostic steps I take when trying to diagnose a bad fuel injector:

1. Find the ‘dead’ cylinder first.
   • If your Corolla is OBD II equipped, this involves connecting a scan tool (or a code reader) and checking for misfire trouble codes.
   • If no codes are registered or your Corolla (Prizm) is not OBD II equipped, the next step is doing a cylinder balance test to find the ‘dead’ cylinder.
2. Check that all spark plug wires are delivering spark.
   1. It's important to make sure that each cylinder is getting spark with a dedicated spark tester.
   2. It's important that you check that the spark plug boot and spark plug are NOT soaked (or swimming) in engine oil.
   3. You should also remove the spark plugs and check them for cracks or carbon tracks (this is SO important).
      • Here's a real life case study on carbon tracks and how they can cause a Misfire: Carbon Tracks Are A Common Cause Of Ignition Misfires (at: easyautodiagnostics.com).
3. Check engine compression.
   1. After making sure that all 4 ignition coils are creating and delivering spark, you need to check for low engine compression.
   2. This is one of the most overlooked tests when diagnosing a misfire or rough idle condition. You can find the test here:
      • How To Test Engine Compression (1.6L Toyota Corolla).
4. Noid light test.
   • If every test above checks out OK, then the next step is to do a fuel injector Noid light test.
   • The Noid light test will help you make sure that the fuel injector is being activated.
   • The following Noid light article/tutorial may help you: How To Use A Noid Light And Where To Buy It (I know that this is not the most in-depth article on the subject, but it should give you an idea of what is involved).
5. Swap the fuel injector with its neighbor on the fuel injector rail.
   1. If I've found out that I have a specific ‘dead’ cylinder and:
      1. The ignition system is not at fault.
      2. That cylinder's compression value is good (compared to the rest of the cylinders).
      3. The fuel injector resistance is good and...
      4. I think the fuel injector is clogged, I then swap out that fuel injector with its neighbor.
      If the misfire now follows that swap, I now know that fuel injector is clogged (or bad) and needs to be cleaned or replaced.

Finding the bad/clogged fuel injector can be a challenge on your 1.6L Toyota Corolla (1.6L Geo Prizm) but it's doable. What will help you save a lot of time, money and frustration is to first find the ‘dead’ cylinder. Following the above diagnostic strategy has saved my lunch quite a few times and I think it'll help you too!

More 1.6L Toyota Tutorials

There are several more ‘how to’ tutorials that I've written that are 1.6L Toyota specific, that may be of further help. You can find the ones that are located here, at this site, by going to the Toyota 1.6L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The Front O2 Heater (1996-1997 1.6L Corolla).
• How To Test The Rear O2 Heater -P0141 (1996-1997 1.6L Corolla).
• How To Retrieve Toyota Corolla OBD I Trouble Codes.
• How To Test The Throttle Position Sensor (1.6L Toyota Corolla).