Skip the auto shop - Our mechanics make house calls

What Does a Spark Plug Do?

Used Spark Plug

Your ignition system is pretty complex, and there are a number of important components that must work with one another to crank the engine and then keep it running. Your spark plugs are among the most important of these, and you have several of them (one per cylinder).

The job of your spark plugs

Spark plugs have a very simple yet essential job. They provide the spark necessary to ignite gasoline in the combustion chamber. Without working spark plugs, your engine will not run (there will be nothing to ignite the fuel and start the combustion process). Your car’s engine basically runs on a series of miniature, contained explosions. First, air and fuel are mixed in each cylinder. When the piston rises toward the top of the cylinder, the spark plug fires. Electricity arcs from the electrode to the tab, and the fuel and air mixture ignites. This creates pressure as the fuel is transformed into a gas (emissions), which pushes the piston back down and turns the engine. This cycle is repeated over and over again in each cylinder of your car.

The engine has one spark plug per cylinder. Each spark plug is connected to a spark plug wire (in conventional and electronic ignitions). The wire runs from the top of the plug to the distributor, which is attached to the coil. However, if you have a distributor-less ignition, you have no spark plug wires. Rather, coil packs are used and the whole system is controlled by the computer.

Over time, your spark plugs wear. This is completely normal. Eventually, they will need to be replaced. The primary form of wear is to the electrode – as the spark plug arcs, it loses tiny amounts of electrode material. Eventually, it shortens. When it becomes too short, it won’t arc properly and the engine will misfire.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...


Related questions

Q: Not sure why car won't start.

Hello, Unfortunately without more information, I will be unable to pinpoint why your Dodge Stratus is not starting. The first step I recommend for all car drivers however is to check your car’s battery. You can do this by turning...

Q: Why do I smell gas in the car?

There could be several reason why your car is smelling like gas. Your car's spark plugs could be very worn out and not firing properly, causing the gas not to be burned properly and creating a gas smell in the...

Q: Engine light staying on

Hi there. The Check Engine Light should stay illuminated until the vehicle is running. So, your light being on while cranking is normal. However, if the light was on before when the engine was running, diagnostic trouble codes may be...