Can You Drive With Bad Spark Plugs? All You Need To Know

Sadly, most people don’t pay attention to spark plugs. Yet, these small parts play a crucial role in your vehicle’s performance.

Now the question is, can you drive with bad spark plugs?

Your car would be unable to run without properly functioning plugs. But, more importantly, you mustn’t drive your car with bad spark plugs. It can damage your vehicle’s engine.

In this case, the safest thing you can do is disconnect the wires of spark plugs. Thus, the electric supply will stop in the spark plugs. Then drive your car to your nearest mechanic shop.

More questions like bad spark plugs symptoms, how often to replace, etc., might have popped up in your mind.

Carefully continue reading the comprehensive guide to learn more.

What Do Spark Plugs Do?

Spark plugs are the small, tiniest, durable bolts of lighting. Every vehicle engine requires a combustion process to run. Spark plugs emit the spark of electricity across a small gap, creating the ignition for the combustion. As a result, our car gets power, stays powered, and creates a smoother burn of the compressed air-fuel mixture by moving the engine pistons.

Remember, spark plugs are made of solid and durable materials. Unfortunately, our vehicle cylinders create excessive heat and pressure. Spark plug’s robust construction effectively withstands significant heat and pressure. Moreover, they are made to burn fuel additives and other contaminant deposits.

Why is this information necessary?

As stated earlier, our vehicle won’t run without the spark. Additionally, car engine performance relies on the spark plug’s health. This means the bad or weak spark plugs cause problems like misfires cold starting when acceleration.

Also, with a problematic spark plug, your vehicle can’t perform at its maximum power. Moreover, fuel economy will also increase.

Can You Drive with Bad Spark Plugs?

Handling a bad spark plug is tough. Even a car will not start due to broken spark plugs.

However, if you are still thinking about whether I should continue driving my car with a bad spark plug?

The straightforward answer is you mustn’t. Instead, it would be best to disconnect the coil wire and visit a mechanic shop. Thus, you can avoid a dangerous situation.

What Causes Spark Plugs to Wear Out?

Generally, spark plugs are wear and tear-resistant. However, at a particular stage, they wear out due to the below reasons.

Oil In Combustion Chamber

Spark plugs start wearing out when engine oil flows in the combustion chamber for a prolonged period. In addition, oil can leak in the combustion chamber, resulting in oily and dirty spark plugs. This can lead the plugs to premature failure.

The oil leak is common in older vehicles. So, keep an eye on whether your vehicle starts to burn more oil than before. An increase in fuel economy is an indicator of the damaged spark plug.


A malfunctioning cooling system and pre-ignition can cause overheating of the spark plug’s tip. Due to pre-ignition, heat buildup occurs in the combustion chamber. It is responsible for spark plugs’ premature failure.

Additionally, improper functionality of the cooling system causes the spark plugs and engine overheating. The electrodes of spark plugs wear out faster because of overheating.

Buildup of Carbon

Dry and black soot on the tip of the insulator and electrode is the indication of carbon-fouled spark plugs. The life expectancy of spark plugs gets reduced because of carbon buildup. As a result, you will experience engine misfires, reduced acceleration, check engine light turn on, and hard starts.

Insufficient Gap in Spark Plugs

A well-calibrated gap between the spark plugs side electrode and center is necessary. This ensures the optimum performance of the engine.

The correct gap guarantees that the arching generates the combustion to burn fuel at the correct voltage and drive the engine.

Spark plug tips will get extra stress if the gap is improper and cause premature wear out.

How to Check Spark Plugs in a Car?

The removal process of spark plugs is pretty simple. But accessing them is a bit challenging. First, however, take assistance from a few tools and check your car’s spark plugs.

Required Tools:

  • 3/8” drive socket set
  • Screwdriver set
  • Combination Set Wrench
  • Small Channellock Pliers
  • Removal tool for Spark Plug Boot
  • 3/8” Drive Torque Wrench
  • Spark Plug Gap Gauge

Step 01: First, the hood needs to be opened. Your belt buckle can scratch the paint if you don’t be cautious. In this case, get a clean bath towel and place it over every fender. Now assess for the best possible way to access the plugs. For this, remove the insulating panels and other covers (if any)

Step 02: Electrical modules, hoses, and wiring harnesses can block access to the spark plugs. Don’t hesitate to remove them.

Step 03: Each spark plug consists of a spark coil when a spark plugs fire incorrectly. When common in modern vehicles. In contrast, each spark plugs top has a single large diameter in old cars.

Step 04: If you own a modern vehicle with spark coils in each spark plug, remove the coils. Each coil will have a low voltage wire attached to the connector. You need to detach this cable too.

Step 05: Pulling the spark plug boot from the plug is the best solution if the spark coil is unavailable. A boot removal tool will be handy and gently wiggle the boot. Avoid gripping the spark plugs associated with wire while pulling off a boot.

Step 06: Remember to use the right universal joint, extension, and socket size while removing the spark plugs. Also, put a tag on each plug to understand what cylinder each plug came from.

How To Know Spark Plug Conditions?

By checking the spark plugs, you can understand the condition of the vehicle engine quite comfortably. Find the below table for your easy understanding.


Overall ConditionSide ElectrodeCenter InsulatorPlug Surface / PartsCause
Normal Combustion ProcessCleanGrayish-yellow or grayish-white to brownN/ALight oil burn. But it is nothing to worry about.
Carbon Fouled N/AN/AEvenly coated with dull black contaminantsi) Dirty air filter

ii) Short distance driving for long hours at low speed

iii) Improper mixture of fuel-air when the engine is starting

Oil Fouled N/A N/ACoat of shiny black or wet componentsi) Combustion chamber is filled with extra oil

ii) Improper functionality of crankcase venting system

iii) Broken valve stem seals

iv) Worn piston rings

Lead Fouling N/AN/A Brownish-yellow glazing coati) Use of fuel or fuel additives that contain lead
Ash Fouling N/A N/ACoat of thick light-colored ceramic-like compoundExtreme use of oil or fuel additives
Melted Center or Side ElectrodeBlistered or softBlistered or softN/A I) Poor quality fuel in the combustion chamber

ii) Overheated plug

iii) Over advanced ignition timing

iv) Incorrect spark plug

Heavily Damaged Center ElectrodeN/A Worn or damaged N/Ai) Too large plug gap

ii) Exceeded service life of plug spark

Severely Worn Side ElectrodeWorn or damagedN/A  N/Ai) Poor quality fuel

ii) Over advanced ignition timing

Fractured Center Electrode Insulator NoseN/A Missing or fractured N/Ai) Exceeded service life of plug spark

ii) Damage in the mechanical parts

 What Are The Symptoms Of Bad Spark Plugs?

Bad, worn, or damaged spark plugs will show a few symptoms. Don’t wait more days to replace them whenever you face these signs.

Rattling Noises: You will hear an unusual knock, pinging, or rattling-like noise once spark plugs start misfiring. The noise is created due to the improper working of the piston and combustion. Typically, the piston moves at high speed. When a spark plugs fire incorrectly, a knocking, rattling-like sound gets generated.

Difficult to Start Vehicle: Your vehicle will take much time to start if the spark plugs health is terrible. You may also feel jerky while starting your car.

Inefficient Performance: Characteristically, spark plug fires when you change the gear or accelerate. If the generated spark doesn’t perform with 100% efficiency, your car will deliver poor performance too. Moreover, you will experience a fuel-wasting drive.

Wastage of Fuel:  Although there are several reasons for fuel wastage, a bad spark plug is one of the common reasons. However, fuel wastage happens when your vehicle doesn’t receive the spark at the right moment.

If you ever experience any of the above issues, let your vehicle be inspected to avoid future complications. A good spark plug is crucial for your vehicle’s optimum performance.

How To Replace A Bad Spark Plug?

Vehicles are available in different models and designs. That is why the spark plug fixing procedure is not universal. In some vehicles, accessing the spark plug is easy, while in others it is difficult. However, the overall process is quite the same.

Here we shared the in-depth process of fixing bad spark plugs.

Step 01: Your vehicle engine can be covered with any object; remove it. Also, keep any cables or ignition coils out of the spark plugs.

Step 02: Spark plugs will be found on the cylinder top. Remove them.

Step 03: While selecting the spark plugs, ensure that the new one has the same length as the older one. Incorrect length will do more harm than good.

Step 04: At the thread of the spark plugs, spray some lube. Next, tighten them up.

Step 05: Then, connect all the parts, cables, or ignition coils that have been removed earlier.

The above steps are a general overview of replacing spark plugs. The process can vary slightly depending on the car model and engine type.

Frequently Asked Questions

How Often Should Spark Plugs Be Replaced?

The good news is; frequent replacement is unnecessary of the spark plugs. Before you need to replace them, they can go several miles and years.

However, most vehicle manufacturers recommend replacing a spark plug after roughly 30,000 miles of the run. The life expectancy of spark plugs relies on their condition and types. For example, copper spark plugs have the shortest service life. On the other hand, durable and rugged material constructed spark plugs are promised to give you many years of service.

Why Do You Need To Replace Lousy Spark Plugs?

A bad spark plug causes the below problems

  • Misfires in the event of acceleration
  • Cold-starting
  • Poor fuel economy
  • Inefficient vehicle performance

Additionally, if you don’t replace the faulty spark plug, your vehicle will not run. So, you have no other choices except to replace it.

Why Are Modern-Day Spark Plugs Durable?

Modern vehicles spark plugs are made of durable and advanced material, allowing them to resist extreme heat and pressure. Iridium, platinum is such a material typically used for manufacturing spark plugs.

As a result, today, spark plugs as long as 100,000 miles without showing major problems or service.

How Far Can You Go With Bad Spark Plugs?

A bad spark plug creates insufficient sparks to start your vehicle. This way, fuel wastage, misfires, etc., happen. Truly, with broken, damaged, faulty, or bad spark plugs, you can’t run your vehicle. However, if your vehicle comes with a multiple-cylinder engine, still driving can be possible with a missing plug.

But the crank will face an unstable situation, which is not suitable for your car at all. More importantly, the longer you drive a car with bad spark plugs, the more pressure you will be putting on your vehicle engine. You are damaging your engine.

Final Words

Undoubtedly, a bad spark plug will surely damage your vehicle engine. So first, check your spark plugs if you are experiencing misfires, harsh acceleration, turn on engine light, etc. Then, replace these spark plugs as soon as possible.

Remember to choose a spark plug compatible with your car type and engine model. You can either go with Iridium, Platinum, Copper, or regular spark plugs according to your preference. Consider the length and size of the bad spark plugs before you replace them with a new one. A wrong size spark plug will also damage your engine.

Hopefully, after reading this comprehensive guide, you know whether you can drive with a bad spark plug? Also, you can now analyze your engine performance by analyzing the physical condition of your spark plugs. Spark plugs are a regular maintenance item, and you need to inspect their health regularly for your vehicle’s superior performance.

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