How To Find The Bad Or Clogged Fuel Injector

The really cool thing about the 4.6L Ford engine, is that all of the eight fuel injectors are easy to get to. This makes it super easy to find out which is the fuel injector that's bad.

Still, troubleshooting a bad feeling doctor when you have a 8 of them can seem quite intimidating . So in this section I am going to share with you my method of diagnosing a bad fuel injector. It's a very simple method that has helped me find the cause behind the misfiring cylinder (whether it's due to a bad fuel injector or something else).

Ok, these are the steps I follow:

  1. Find the ‘dead’ cylinder first.
    1. Half the battle is won if you can find the ‘dead’ cylinder. In other words this is the most important troubleshooting first step. If your Crown Victoria (Grand Marquis) is OBD II equipped, then all you need to do is check for misfire trouble codes.
    2. If your Crown Vic is not OBD II equipped, then you'll need to do a manual cylinder balance test to find it.
  2. After identifying the ‘dead’ cylinder, make sure it's getting spark.
    1. It's important that you check the tower (of the ignition coil pack assembly) for spark with a dedicated spark tester.
      1. Here's a tutorial that'll help you test the ignition coil packs on your 4.6L Ford Crown Vic: How To Test The 2 Coil Packs (Ford 4.6L V8).
    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).
      1. 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. If the ‘dead’ cylinder has spark, the next step is to make sure it has good compression.
    1. After making sure that the ‘dead’ cylinder's plug wire is 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:
      1. How To Test Engine Compression (Ford 4.6L, 5.4L).
  4. If the ‘dead’ cylinder has spark and good compression, the next step is a fuel injector Noid light test.
    1. If every test above checks out OK, then the next step is to make sure that the fuel injector is being activated.
    2. 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. If the ‘dead’ cylinder has spark, good compression, and is being activated; the next step is swap the fuel injector.
    1. If I've found out that I have a specific ‘dead’ cylinder and:
      1. It's getting spark, that it's spark plug is not soaked in oil or anti-freeze.
      2. It has good compression.
      3. The fuel injector resistance is good and is being activated by the fuel injection computer...
      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.

As you can see, finding the cause of the misfire boils down to a process of elimination. As you start off by identifying the ‘dead’ cylinder, the next steps are too make sure that its getting spark, good compression, etcetera.

Where To Buy The Fuel Injector And Save

The following links will help you to comparison shop for a fuel injector:

Not sure if the above fuel injectors fit your particular 4.6L Ford Crown Victoria (4.6L Mercury Grand Marquis)? Don't worry, once you click on the links and arrive on the site, they'll make sure it fits! If it doesn't, they'll find you the right one.