How to Tell if It Is Time to Replace Spark Plugs

Spark plugs ignite the air/fuel mixture within your automobile's combustion chamber. They don't last forever and often go bad long before their projected life spans. If your car suddenly starts roughly when you crank it up, your spark plugs could be bad. To ensure your car starts and works properly, pay attention to signs that your spark plugs need to be replaced.

Instructions

1. Check your vehicle's odometer. You typically should replace your spark plugs about every 30,000 miles, despite an advertised life expectancy of up to 60,000 miles on an average plug.

2. Look for signs of spark plug damage regardless of your car's mileage. If your car misfires or you have difficulty starting it, you could have a spark plug problem. If you experience poor fuel mileage, rough start or rough idle, poor acceleration or stalling, your spark plugs may need to be replaced.

3. Take your automobile to a mechanic if you suspect your spark plugs need replacement. Ask the mechanic to put your vehicle on an oscilloscope and look at the secondary ignition pattern. Badly worn plugs will cause the firing voltage to shoot up to the maximum output of the coil. Your spark plugs need to be changed if the pattern shows initial secondary spikes approaching the upper voltage limits of the system.

Tips & Warnings

• Consider replacing worn plugs with premium long-life platinum or indium spark plugs. They cost more, but they typically last longer.

References

• www.AA1Car.com: Why spark plugs need to be replaced

Resources

• Car Talk