How To Troubleshoot a Misfire (Suzuki 1.3L, 1.6L, 1.8L, 2.0L, 2.3L)

Ignition System: Misfire Troubleshooting

Since the ignition system is usually the culprit behind most misfire conditions, this is where you should start your basic tests.

Here are my suggestions:

1. Check for misfire codes with a scan tool.
   • The misfire code will let you know which cylinder is the one that's dead.
   • If no codes are present or you have a P0300, then you'll need to do a cylinder balance test.
     • The cylinder balance test should be done by unplugging the electrical connector of the fuel injector or the COP coil.
2. Physically inspect things.
   • Check the spark plugs for:
     • Cracks.
     • Engine oil (from a leaking valve cover gasket).
     • Fuel fouling.
     • Center electrode capped/blocked with carbon.
     • Check for carbon tracks on the ceramic insulator.
   • Check the COP coils or spark plug wires for:
     • Cracks or burns on the rubber boot that connects/surrounds the spark plug.
     • Engine oil (from a leaking valve cover gasket).
     • Carbon tracks on the inside of the rubber boot.
   • Check the distributor cap (on distributor type ignition systems) for:
     • Engine oil (from a leaking from the internal distributor shaft seal).
     • Cracks and/or carbon tracks on the inside the cap.

3. Test for spark.
   • Use a dedicated spark tester.
     • Doing a spark test with anything other than a spark tester (like pulling the COP coil or spark plug wire from the spark plug) can and will damage the ignition coil.
     • Using a timing light will only have you wasting your time and money since this is the MOST INACCURATE way to test for spark.

Fuel System: Misfire Troubleshooting

Dirty and/or clogged fuel injectors will spray fuel in a jet instead of a fine atomized mist. In extreme cases, this will soak and foul the spark plug with gasoline and the spark plug won't spark anymore.

Most of the time though, clogged fuel injectors create a rough idle and lack of power condition due to the lean air/fuel mixtures they create in the cylinders.

Here are some of the tests you'll need to do:

1. Fuel Injector Tests.
   • Confirm that the fuel injector is being activated or not with a Noid light.
   • Check that the fuel injector is not fried with a simple resistance test and then comparing its resistance value to the other four.
2. Fuel Pump Tests.
   • Check the fuel pressure with a fuel pressure gauge.
   • A fuel pump putting out a low fuel pressure (even if it keeps the engine running) will cause a lean condition that will cause misfires and/or a rough idle condition.
3. Fuel Pressure Regulator Tests.
   • The most common failure is the fuel leaking out of the vacuum hose inlet nipple.

Maintenance, like replacing the fuel filter, adding fuel injector cleaner to the gas tank are key to keeping the fuel injectors clean and happily injecting the correct amount of fuel.