Symptoms Of Bad or Failing Spark Plugs

Every car owner wants their vehicle to perform at an optimal level and in order to achieve this goal, proper maintenance must be applied to every part of the car — even to the unassuming spark plugs.

A spark plug may be small, but it is an incredibly important piece of equipment: Its job is to start the car. The spark plug does this by creating a spark which in turn ignites the air-fuel mixture in the combustion engine.

The spark plugs send the engine’s pistons into action, and then they go on to provide the power necessary to keep the vehicle in motion as it makes its way down the road.

Timely and appropriate car care not only improves a vehicle’s life span, but also creates a much better driving experience overall. If a car owner forgets to take their car in for a regular tuneup, the vehicle may start to exhibit signs that it needs some attention.

Symptoms Of Bad Spark Plugs

Symptoms Of Bad Spark Plugs

Symptoms of bad spark plugs can include:

  • Reduced gas mileage
  • Lack of acceleration
  • Trouble Starting
  • Engine misfires
  • Rough idling
  • Check Engine Light Comes On

#1. Reduced gas mileage.

Making more trips to the gas station? A sudden drop in fuel economy can be traced to dirty or fouled spark plugs. If the spark plugs aren’t functioning properly, it can have a negative impact on your gas mileage.

#2. Lack of acceleration.

Imagine that a car owner is traveling down the road and then tries to accelerate but the car won’t respond. Not only does this create a very dangerous predicament, but it also should alert the owner that the car needs to be seen by a mechanic.

The car’s failure to accelerate is a very obvious sign that the spark plugs need to be replaced. Such scenarios can be avoided through scheduling regular car checkups.

#3. Trouble Starting.

When a car will not start, usually the battery is thought to be the aggravating cause behind this issue; however, the spark plugs should also be high on the suspect list. If spark plugs have become clogged or worn down, the car’s engine has to work overtime in order to make up for the overworked plugs.

Sometimes the car will not start at all because there is simply not enough spark created to turn the engine over. When the spark plugs are in this sad state, even harsh weather conditions can keep the engine from turning over.

#4. Engine Misfires.

Many things can cause an engine to misfire, like inferior quality fuel or leaky valves, but those offenders may not be the only causes behind this particular issue though. An engine misfire can often be the result of at least one timeworn spark plug.

When this happens, a car owner will notice that the engine pace wavers but then catches back up. They may also hear a “pop” from the engine when it falters before recovering the proper timing.

When a vehicle misfires, raw fuel is sent into the exhaust. Ultimately, this causes damage to the catalytic converter and can result in costly repairs.

#5. Rough Idling.

When your spark plugs are performing as they should, your engine sounds smooth and steady. A fouled spark plug causes your engine to sound rough while idling. You might also feel the vehicle vibrating.

#6. Your Check Engine Light Comes On.

Worn/failed spark plugs, coil packs, or spark plug wires can trigger your check engine light to come on. In today’s cars, if a spark plug fails and can no longer ignite the air-fuel mixture, then the most obvious event should be the check engine light coming on or even flashing.

This can cause your engine to misfire and your check engine light to pop on. A flashing engine light could mean that potentially catastrophic misfires are taking place, which could damage the catalytic converter(s).

In general, it’s best to replace spark plugs as part of preventative maintenance based on the manufacturer’s suggested maintenance schedule.

How Long Do Spark Plugs Last?

In any car care matter, it’s always best to follow the Manufacturer Suggested Maintenance Schedule. Review your vehicle’s suggested maintenance schedule to see when to replace your spark plugs.

Luckily, spark plugs don’t wear out very quickly. You can typically get 80,000 miles on them before they need replacing. But if you notice any of these symptoms, it’s time to get your spark plugs checked out with an engine tune-up.

What Does A Bad Spark Plug Look Like?

So, how can you tell if a spark plug has lost its pep? There are a few visible signs you can spot to single out a bad spark plug:

  • Carbon buildup: Look for debris built up around the tip of the spark plug. Sometimes simply removing and cleaning off a dirty spark plug with an abrasive, like a wire brush or Brillo pad, will make it good as new. But, if you notice black oil buildup around the spark plug, this may be a sign of a bigger problem like an internal engine oil leak
  • A worn electrode: At the bottom of the spark plug, the part screwed into the combustion chamber, is a small metal piece that looks like a dome with a J-shaped piece of metal over it. The J-shaped piece is the ground electrode, and the dome is part of the central electrode that runs the length of the spark plug. These electrodes will wear after years of igniting air and fuel in the combustion chamber. Melting and erosion around these electrodes is a sign a spark plug has gone bad.
  • A cracked insulator: Take a look at the insulator. It’s the white ceramic casing extending from the seal to the terminal of a spark plug. Cracks and chips, even as slight as a hairline crack, can prevent a spark plug from controlling the flow of electricity through the terminal to power your engine. A cracked insulator cannot be fixed, and the spark plug will need to be replaced.

The main point every owner of a car should take away from this article is to be aware of the car’s preemptive warning signals. It is easy to pass over a routine maintenance appointment but when the vehicle sounds off its alerts, it is in a car owner’s best interest to pay attention.

The one thing a car owner can always bank on is this: failing to clean or replace overworked spark plugs can result in costly repairs that could have been avoided.