How to Tell If Your Spark Plugs Need to Be Replaced

Spark plugs are important maintenance items that should not be overlooked or neglected. They play an important role related to engine performance, fuel mileage and exhaust emission standards. The best way to determine when spark plug replacement is needed is the maintenance schedule for your specific vehicle. The life expectancy of spark plugs will vary widely based on the vehicle and engine designs and spark plug type. If you are not the original owner of the vehicle and unaware of its maintenance history, there are some additional indicators to consider.

Signs to Tell If Your Spark Plugs Need to Be Replaced

1

Visual Inspection

Remove and compare your old spark plugs to a new one. If the tip and/or electrode show excessive wear they should be replaced. Also, look for fuel and oil contamination. If contamination is found, the spark plugs should be replaced. However, additional inspection is needed to determine the cause of the contamination whether it is caused by oil, fuel, or coolant. Failing components within the engine itself can cause oil or coolant contamination. Fuel contamination can be caused by failing components within the fuel, ignition and/or emission systems.

Pro Tip: The following are symptoms that may occur with worn spark plugs. Keep in mind, there may be other issues causing the problem. Be sure and do a complete inspection before replacing any parts.

2

Trouble Starting

If you are experiencing what seems to be longer cranking times, especially on a cold morning, you'll want to look at your spark plugs and related ignition and fuel system components. Over time, spark plugs develop residue from unburnt gases and oils, which reduces your car's performance and makes cold-starting more difficult. Tough cold starting is not only bad for your engine, but can also drain the battery and increase starter wear and tear.

3

Rough Idling

If your vehicle's engine is running rough or noisy when idling, you may have a spark plug issue. Heavy rumbling when waiting at a stoplight or in a drive-thru may indicate your car is overdue for maintenance. Inspect the spark plugs and replace accordingly. Replacing the spark plugs, and potentially also the ignition coils and wires, may solve this.

4

Misfiring

Misfires are hard to miss, as the engine will shake so badly that you'll feel the vibration throughout the car. Misfiring results in poor performance, reduced fuel economy, increased emissions, and rough idling. Replacing spark plugs may help with this issue but inspect them first.

5

Decreased Fuel Mileage

Low gas mileage is a subtler sign of worn spark plugs. Deteriorated spark plugs can account for as much as a 30-percent loss in fuel economy, which you'll definitely feel at the pump and your wallet. If you've checked and determined the fuel mileage has dropped, check your spark plugs and related items for signs of wear.

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