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:
- 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.
- 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.
- 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.
Engine Mechanical: Misfire Troubleshooting
The pistons and cylinder head valves are the ones that are responsible for the ‘Air’ part of the equation.
If the engine is unable to compress the air, that it's breathing, your car is gonna' experience a misfire (rough idle) that no matter what you replace, the rough idle will persist.
Engine burning excessive amounts of engine oil which will cause carbon build up on the spark plug's center electrode, eventually stopping spark.
Other engine mechanical problems are: vacuum leaks, dirty throttle plate and throttle bore. Here are some specific tests that you may have to look into and perform:
- Engine Compression Test.
- This will confirm if the misfire or rough idle is due to burned or severely worn cylinder head valves or piston rings.
- Vacuum Leak Tests.
- Physically check all vacuum hoses for dry rot, tears, and holes.
- Spraying carb. cleaner spray around the areas where the manifold bolts to the cylinder head (with a cold running engine) to pinpoint leaking intake manifold gaskets.
- Inspect and clean the throttle body.
- Carbon deposits can accumulate on the throttle plate and bore and cause idle quality problems.
- Cleaning should be done with a toothbrush and an approved throttle body spray cleaner.
Related Articles
You can find a complete list of Suzuki test articles here: Suzuki Index Of Articles.
Here's a list of articles you'll find there:
- How To Test The Ignition Coils Suzuki: Swift, Vitara - Chevy: Metro, Tracker.
- Blown Head Gasket Test.
- How To Test The 2.5L COP Coils.
If this info saved the day, buy me a beer!
