What Does A Bad Spark Plug Look Like – Know Your Engine

What does a bad spark plug looks like

You are still wondering how to identify bad spark plugs just by looking at them? Then let us tell you, it is the most straightforward job to do. Even if you know nothing about vehicle parts, these symptoms are pretty easy to understand. Readout further to more!

What Does A Bad Spark Plug Look Like

4 Signs to identify bad spark plugs:

The outer part looks burnt

Die to excessive overheating, the spark plugs get burned from the outside—also, some of the internal and external wires burn, which are negligible to the eyes.

Insulator looks carbon-fouled

At first glance, you will see the insulator tips look soot-black due to excessive carbon buildup. It is the result of inefficient spark plugs.

Signs To Identify Bad Spark Plugs

Electrodes get broken

When you notice the electrodes broke, you know those spark plugs are not for your vehicle. Hence, they couldn’t function to that potential.

Worn out exterior

With time, the spark plugs wear out and looks rusted from the outside. It means they are about to stop working and need replacement.


Carbon fouled spark plug

carbon fouled spark plug

What causes a spark plug to turn black – oil deposits

What causes a spark plug to turn black

What does a good burning spark plug look like?

What does a good burning spark plug look like

Frequently Asked Questions

#1. Is it bad to drive with faulty spark plugs?

If you know your vehicle’s spark plug has gone bad, it is better to drive with it anymore unless you change them. The car’s engine will stop working if you continue driving with bad spark plugs.

#2. What happens when one spark plug goes bad?

Some primary symptoms that bad spark plugs give out are slower acceleration, poor fuel economy, rough starting of car and engine surging.

#3. How long does a spark plug last?

An average to good-quality spark plug lasts up to 80k-100k mileage, depending on the type of vehicle. However, this may vary in different manufacturers, and mileage can be high in top-notch models.


Lastly, we want to tell you that if you see any of those symptoms on your spark plug, contact a mechanic and get them replaced if needed. Do keep a maintenance routine for spark plugs to increase their life.

You won’t like rough and unsteady car drives, right? So, get them replaced once and for a long time.