How to Tell If a Spark Plug Is Bad? – signs of bad spark plug

Without operational spark plug in the car, you will have to face poor ignition and bad electric conduction. Certainly it creates hindrance while starting the car. But how to tell if a spark plug is bad is a valid question every car owner must know.

As you know, spark plug in the car or any vehicle is there to spark the electricity that further ignites the combustion in the engine. It also takes care of the fuel mileage and exhaust emission standards. So when the spark plug is bad, it fails to ignite due to fuel residue on it.

One of the quick and easiest ways to tell if the spark plug has gone bad is comparing it with the older one. Also you need to check if there is any oil contamination or not. The contamination on the spark  plug is usually the reason for bad performance.

The fuel residue on the plug can cause moisture or dampen it which then makes the spark plugs inefficient to ignite. There are many more signs that tell you, it’s time to replace the spark plug. 

Let’s now find the signs of bad spark plug.

Signs of Bad Spark Plug 

Luckily, when the spark plug is bad, it gives you signs for timely replacement. Below are the most common indications that you will notice if your car has poor spark plug.

1. Car won’t start

The most obvious sign of a bad spark plug is that the car won’t start. This is because the spark plug is not sending the current for combustion and you will notice longer cranking noise on chilly mornings. This can be accumulated due to residue from the unburnt gasses and oils.

2. Noisy engine when idling

The engine has rough running performance when idling, it can be due to a poor ignition system in the car. However the intense rumbling means the care needs maintenance. When there is a spark plug issue, it means that the spark plug or the ignition coils need to be changed.

Read Also: Why Check Transmission Fluid When Engine Is Running

3. Misfiring of engine

Another sign of bad spark plug is misfiring. When this happens, the engine shakes and vibrates so that the car gets its visible impact. The bad spark plug causes reduced fuel economy, increased emissions, and rough idling so consider replacing it.

4. Low mileage

If the spark plug is bad, your car will give low gas mileage. Usually, the spark plugs that are not durable, or have faulty performance are likely to let out 30% loss in fuel economy

5. No acceleration

Acceleration in the car is what keeps it going. If you are noticing there is no acceleration in your car, it is another sign that the spark plug has gone bad. The most common reason for that are the dirty plugs and it fails to cause a spark.

6. Hard car start

If your car is not starting it can be due to zero gas/fuel, dead battery and the bad spark plug. So check the plugs and replace them if they need.

Can I drive with a bad spark plug?

If you drive when the spark plug is bad, it can cause some serious damage to the vehicle. Since the spark plug has to maintain the ideal current flow when it fluctuates, it can cause further damage. Also driving with the spark plug is poor, faulty, or bad, it can damage the catalytic converter and that would be costly to repair.

What to do when a spark plug is bad?

If cleaning then does not help, you should not compromise on replacing the bad spark plug. You need to make sure the spark plugs have not exceeded the expected durability life. If so, consider replacing them with new ones.

If your car has the common spark plugs (made with copper and nickel), consider replacing them after every 30,000 to 50,000 miles or so. You can also check the spark plug manufacturer for the right information.

But if your car has Platinum and iridium spark plugs that are more durable and offer ideal performance, you can replace them after every 60,000 to 150,000 miles, or as the manufacturer says.