Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. What Does a Spark Plug Do?

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

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...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...
P0291OBD-II Trouble Code: Cylinder 11 Injector Circuit Low
P0291 code definition When your vehicle’s PCM registers the P0291 code, it means that a voltage reading came from the fuel injector circuit – for cylinder number 11’s fuel injector –...

Related questions

Q: Q: Car stalls when I stop.

Having your Maxima stall while stopping can make it difficult to ever want to stop driving! Typically when I see a vehicle with these similar symptoms it leads me to consider two common possibilities, a dirty throttle body and problems...

Q: Misfiring - 2010 Chevrolet Cobalt

A misfire can be caused for several reasons such as bad plugs (which you have fixed), detonation (bad timing), bad ignition coil, vacuum leak, faulty fuel injectors, low fuel pressure or faulty spark plug wires to name a few. This...

Q: Engine kicking on startup when it's cold

The first thing you'd want to do is check the ignition timing. It is possible that it is too far advanced. If it is too far advanced, odds are, it's going to need a timing chain, which can be...