Symptoms of Faulty or Faulty Spark Plugs

Common signs of bad spark plugs include slow acceleration, loss of power, poor fuel economy, engine misfiring, and difficulty starting the vehicle.

Without a spark, the fuel could not ignite in the combustion chamber. Spark plugs have been an important component of the internal combustion engine for many years. Spark plugs are designed to transmit an electrical signal sent by the ignition coil at a predetermined time to create a spark that ignites the air/fuel mixture inside the combustion chamber. Every vehicle requires a specific type of spark plug, made from specific materials, and with a designated spark plug gap set by the mechanic at the time of installation. Good spark plugs will burn fuel efficiently, while bad or faulty spark plugs can cause the engine to not start at all.

Spark plugs are similar to engine oil, fuel filters, and air filters in that they require regular maintenance and repair to keep the engine running. Most cars sold in the US require spark plugs to be replaced every 30,000 to 50,000 miles. However, some new cars, trucks, and SUVs have advanced ignition systems that supposedly make it unnecessary to change spark plugs. Regardless of any warranties or claims made by the vehicle manufacturer, there remain situations where a spark plug wears out or shows signs of failure.

Listed below are 6 common signs of worn or dirty spark plugs that should be replaced by an ASE certified mechanic as soon as possible.

1. Slow acceleration

The most common cause of poor acceleration in most vehicles is a problem in the ignition system. Today's modern engines have several sensors that tell the on-board computer and ignition system when to send electrical pulses to fire the spark plug, so a faulty sensor could be the problem. However, sometimes the problem is as simple as a worn spark plug. A spark plug is made up of materials that work together to produce a spark hot enough to ignite the air/fuel mixture. As these materials wear out, the efficiency of the spark plug decreases, which can significantly reduce vehicle acceleration.

If you notice that your car is running sluggish or not accelerating as fast as it used to, it could be due to a faulty spark plug that needs to be replaced. However, you should see a mechanic to have this problem checked as it can be caused by a variety of other factors, including bad fuel filters, a dirty or clogged fuel injector, or problems with the oxygen sensors.

2. Poor fuel economy

A fully functional spark plug helps burn fuel efficiently in the combustion cycle. When this happens, your vehicle may achieve above average fuel economy. When a spark plug is not performing optimally, it is often because the gap between the spark plug electrodes is too small or too large. In fact, many mechanics take the spark plugs out, inspect them, and adjust the gap to factory settings rather than completely replacing the spark plug. If your car is experiencing increased fuel consumption, it could very well be due to a worn spark plug.

3. Engine misfires

If the engine misfires, this is usually due to a problem in the ignition system. In modern vehicles, this is usually due to a sensor malfunction. However, it can also be caused by damage to the spark plug wire or spark plug tip that connects to the wire. Engine misfiring can be noticed by intermittent stumbling or hissing engine sounds. If the engine is allowed to misfire, exhaust emissions will increase, engine power will decrease, and fuel economy will decrease.

4. Bursts or oscillations of the engine

You may notice that the motor oscillates as it accelerates. In this case, the engine reacts incorrectly to the actions of the driver. Power can increase dramatically and then slow down. The engine sucks in more air than it should during the combustion process, resulting in a delay in power delivery. A combination of hesitation and spikes may indicate a problem with the spark plug.

5. Rough idle

A bad spark plug can cause your engine to make a harsh sound at idle. The shaking sound engulfing the car will also cause your car to vibrate. This may indicate a spark plug problem where the cylinder misfires only occur at idle.

6. Difficult to start

If you're having trouble starting your car, it could be a sign of worn spark plugs. As noted above, an engine's ignition system is made up of several separate components that must work together in order to function properly. At the first sign of trouble starting your car, truck, or SUV, it's a good idea to see a certified mechanic to find out the cause.

Regardless of what the problem might be, you may need new spark plugs when yours wear out over time. Proactive spark plug maintenance can extend the life of your engine by hundreds of thousands of miles.