The Best Car Engine Upgrade!
Best Car Engine Update

Bad Spark Plug Symptoms

(4/5)  29 votes

Spark plugs are very important element of the vehicle's engine. Although it is quite abandoned part of the engine spark plugs are critical for normal vehicle running. Spark plugs are composed of a central conductor, an insulator and a shell. Its mission is to inflame with an electric spark mix of fuel and air. This process starts the engine and allows it to work correctly. Hence, spark plugs are critically important for fuel economy, good combustion and engine performance.

But the main thing that provides spark plug is uninterrupted movement of a vehicle. Drivers should remember that cleaning absence may cause plug failure, that will result a lot of problems. There are some common bad spark plug symptoms.

Spark plugs

The Most Common Symptoms of Bad Spark Plugs

Starting Trouble

The most common symptom of bad spark plugs is engine's starting troubles. The engine can’t start even after several attempts. The reason of this problem may be that the spark plug fails to produce the spark. Faulty spark plugs may cause rapid discharge of the battery, so this spark plug need to be replaced.

Rough engine idle

If your vehicle is bouncy when the engine is running and makes more vibration as well, it might signify that your vehicle's "heart" stumbles. It is common symptom of a bad spark plug, so we recommend you to check it out until it's too late and until repairing becomes too expensive.


Engine misfire is easy to identify: if your vehicle's engine stops during driving and then attains pace, it is engine misfire. Even if one of the cylinders interrupts the firing, your engine will misfire. It means one of the spark plugs doesn’t work correctly. During the misfire your vehicle emits more contaminated exhaust gases.

Engine surging

Engine surging or engine hesitation is an obvious symptom of the bad spark plug as well. When it happens your vehicle makes sharp jerks first and then slows down. This problem decreases engine power and might be dangerous in massive traffic on the road.

Low mileage

This symptom affects fuel economy. Bad spark plug decreases engine's performance and increases fuel consumption, so the mileage decreases.

Poor acceleration

One more bad spark plug symptom that is easy to identify is poor acceleration. It seems like engine executes your commands with delay and the engine performance is hampered. Pushing the acceleration pedal down doesn’t boost your vehicle immediately.

Bad spark plug vs good
Bad spark plugs

Bad spark plugs usually decrease car performance and may even cause damage of it. So when to replace spark plugs? It depends on the type of spark plug and materials it is made from. In general, copper spark plugs require replacement every 20,000 miles. Platinum and iridium spark plugs have better longevity, their lifespan varies from 40,000 to 60,000 miles. Although, it is a good practice to check your spark plug for the most common problems. There are some recommendations.

How to check a spark plug

  1. 1. Pay attention to the fuel consumption of your vehicle. If you note that it is seriously increased, we recommend you to check the spark plugs.
  2. 2. Look at the spark plugs.
    •     a) if there is deposits of fuel or carbon you should replace spark plugs immediately.
    •     b) if the color of plugs isn't grayish or of a light tan, it means that your vehicle is functioning at abnormal temperature. It may cause serious damage, so we recommend you to replace spark plugs as fast as possible.
    •     c) if the brim of the electrode look like a sharp point, it means that the spark plug is completely used and requires replacement.

These simple recommendation will help you you to understand when to change spark plugs to prevent damage of your vehicle and enjoy driving.