Spark Plug Problems – Troubleshooting, Failure Symptoms, Replacement.

Spark Plug Problems - Troubleshooting, Failure Symptoms, Replacement.
Spark Plug Problems - Troubleshooting, Failure Symptoms, Replacement.

All spark plugs wear out as they age and at some point, will cause spark plug problems.

So, after enduring abuse for thousands of miles, you really can’t expect them to last forever.

Good spark plugs will burn fuel efficiently. While, bad or failing spark plugs, can cause a number of problems.

Therefore, if you are having any spark plug problems; the first thing to happen is, reduced or no spark at all. Without a proper spark, there would be no way, for fuel to ignite in the combustion chamber. All spark plugs require routine service and maintenance, to keep your engine running strong.

Usually, your car can go for years and several miles; before you have to worry about, getting new spark plugs. Spark plugs have been, a critical component of the internal combustion engine for years.


Most spark plug problems happen, because of deposits from the combustion process. The deposits that form on the spark plugs, can result in pre-ignition of the fuel. This translates to, an unreliable supply of energy for your vehicle.

Carbon Deposits On Spark Plugs
Carbon Deposits On Spark Plugs

Additionally, another reason why spark plugs can’t last for a really long time is its exposure to:

  • Debris
  • Extreme temperatures
  • Normal wear and tear
  • Damage
Spark Plug Damage
Spark Plug Damage

These things, increase the gap or space, where the spark has to travel.

The Spark Plug, Has Two Primary Functions:

  1. Electrical energy from the ignition coil, is transmitted through the spark plug; jumping the gap creating a electrical spark. This electrical spark, ignites the gasoline/air mixture in the combustion chamber.
  2. Spark plugs also, remove heat from the combustion chamber. Spark plugs cannot create heat, they can only remove heat. The temperature of the end of the plug’s firing end, must be kept low enough to prevent pre-ignition. But, high enough to prevent fouling. The spark plug works as a heat exchanger, by pulling unwanted thermal energy from the combustion chamber. As a result, transferring heat, to the engines cooling system.

How Do You Pick, The Correct Spark Plug For Your Engine

Check Your Car’s Manufacturer For Proper Parts
Check Your Car’s Manufacturer For Proper Parts

One of the most common problems car owners experience, when it comes to changing spark plugs is; knowing what spark plug to buy. There are just so many to pick from.

The obvious solution is, to check your car’s manufacturer and see what type they recommend. The manufacturer knows best, what your car’s engine needs and what spark plug can meet those needs exactly.

Spark Plug Failure Symptoms

The spark plug is a major part of the ignition system. Because, it keeps the engine running, by constantly igniting the fuel-air mixture.

Engine Misfire

Failing Plugs Causing Misfire
Failing Plugs Causing Misfire

The engine will appear to stumble for a brief period of time and then regain its pace. This is most recognizable when accelerating or when the car is in idle. Failing spark plugs, can cause the car engine to misfire and thus affect its performance. Misfiring will cause, increased exhaust emissions, reduced fuel economy and reduced engine power. A single misfiring spark plug, can dump enough raw fuel into the exhaust; to overheat and damage the catalytic converter.

Excessive Fuel Consumption

Spark plug problems, might cause your engine to consume more fuel than usual. As the (ECM) has no control over spark strength or oxygen content; it adds fuel to compensate for poor combustion. A properly functioning spark plug, helps to ensure the emissions from your vehicle, are kept at a minimum.

Deteriorated spark plugs, can decrease your vehicle’s fuel economy, due to incomplete combustion. As your spark plug wears, the gap between the plug electrodes can either, expand or close up. Either of these conditions, can negatively affect your engine’s fuel economy and emissions.

Poor Acceleration

On acceleration, spark plug are under particular demand, to deliver a strong spark. Also, to ignite more fuel and generate more power. Faulty spark plugs or weak ignition coils, may not keep up with the demand. Examples of poor acceleration include, a lack of responsiveness or delayed reaction, when pressing your gas pedal. In this situation, pushing down on the gas pedal, does not immediately boost the speed of the vehicle. Also, it will appear like, the engine is being overworked.

Rough Engine Idle

At idle, spark plug problems, might be evident as more a vibration. Uneven idling and vibrations, is a major warning sign that indicates faulty spark plugs. Failing spark plugs can result in, the engine running rougher and producing vibrations when left at idle speeds. An engine with properly performing spark plugs, should sound continuous and smooth. If your spark plugs are not working as they should; your engine will produce a rough and jittery sound and your engine will stumble.

Hard Starting

Faulty spark plugs, can cause the car to exhibit starting troubles. Worn out plugs, do not produce sufficient spark, which is needed for starting the engine. This results in engine stalling and fail to start quickly. Besides, failing spark plugs, will also take its toll on the battery life. And, normal functioning of the ignition system. Proper ignition is most difficult, when the engine is “cold.” The (ECM) adds more fuel to account for poor vaporization. Which can be difficult for a worn spark plug to ignite. Resulting in hard starting, long cranking, or a no-start condition.

Check Engine Light

For many people, the check engine light, might be the only sign; your engine is having spark plug problems. The (ECM) is far more sensitive than many drivers and can, detect a single cylinder misfire. If you get a check engine light along with slight jolts while accelerating, the spark plugs could be to blame.

Always check to condition of the old spark plugs. They will show you, what was happening in your engine and other warning signs.

Basic Spark Plug Replacement

Spark Plug Replacement Tools
Spark Plug Replacement Tools

Depending on the vehicle, engine, and spark plug type; spark plugs generally last, from 30,000 to 120,000 miles. For most vehicles, replacing spark plugs, is a simple job. All though you might need to be a contortionist, to get to some of them. Because, they might be placed, behind shields or under intake manifolds and other equipment.

Here Are The Basic Steps To Replace Spark Plugs:

First, Get Access To The Spark Plugs

This might require, removing other parts, such as engine covers, heat shields, or the intake manifold.

Remove The Spark Plug Wires And Or Ignition Coils

Before removing wires, use tape or some other means, to mark their correct locations. Replace scuffed, worn, or damaged spark plugs wires or boots.

Use Compressed Air To Blow Out Spark Plug Holes

Debris tends to collect, in unprotected spark plug tubes and channels. Using compressed air, is a good way to get rid of it. Also, preventing it from falling into the cylinder, when you remove the spark plug.

Remove The Spark Plugs

Using a spark plug socket, remove the old spark plugs.

Recheck The Spark Plug Gap

Most new spark plug gaps, are preset from the factory. But, it’s a good idea to check and adjust the spark plug gap, just to be sure.

Lubricate New Spark Plug Threads

Using just a dab of anti-seize lubricant, silver or copper doesn’t matter; lubricate the spark plug threads and gasket.

Install The New Spark Plugs

New Spark Plugs
New Spark Plugs

Turn the new spark plug in, by hand until finger tight, then torque to specification. Gasket types, usually specify a quarter- to a half-turn after contact. While, non-gasket types, specify just a sixteenth-turn. Check the manual to be sure.

Reinstall Everything Else

Finally, reinstall wires/coils and all other parts. Such as engine covers, heat shields, or the intake manifold. Being observant, is key to keeping a reliable car. And, recognizing spark plug problems early, can improve fuel economy and prevent you from being stranded.

Oil Fouled Plugs
Oil Fouled Plugs


So, knowing what happens, when spark plugs go bad, is essential to knowing when to get replacements. Because, the signs of spark plug are pretty obvious. Consequently, you should recognize these signs of a bad spark plug as soon as they appear. So, by being proactive about spark plug maintenance; you can extend the life of your engine, by hundreds of thousands of miles.

Thank You !