Skip the auto shop - Our mechanics make house calls

What Causes Spark Plugs to Wear Out?

Worn Out Spark Plugs

Without operational spark plugs, your engine won’t run. If even just one plug were to fail, the change in functionality would be very noticeable. Your engine would run rough, it would idle poorly, it might spit and sputter during acceleration, and it might even stall out on you. Spark plugs do wear out over time, although the actual lifespan varies depending on the type of plug in question, the condition of your engine, and your driving habits.

Wear factors for spark plugs

There are several factors that play a role in spark plug health, but the most common reason for them to wear out is that they’re just old. To understand this, you need to know a bit more about how spark plugs work.

When your alternator generates electricity, it is sent through the ignition system, down the spark plug wires, and to each individual spark plug. The plugs then create electrical arcs at the electrodes (the small metal cylinders protruding from the bottoms of the plugs). Each time a plug fires, a minute amount of metal is removed from the electrode. This shortens the electrode, and requires more and more electricity to create the arc necessary to fire the cylinder. Eventually, the electrode will be so worn that it won’t arc at all.

This is what happens in a normal, properly maintained engine. There are other factors that can reduce plug life (all spark plugs eventually wear out; it’s just a question of when).

  • Overheating Damage: Overheating spark plugs can cause the electrode to wear faster. Pre-ignition from an improperly timed engine can cause this, as can an incorrect air to fuel ratio.

  • Oil Contamination: If oil seeps onto the spark plug, it will foul the tip. This creates damage and additional wear (oil seeping into the combustion chamber is something that happens over time as seals begin to fail).

  • Carbon: Carbon buildup on the tip can also cause premature failure. This can happen due to dirty injectors, a clogged air filter and many other reasons.

As you can see, there are a number of different factors that affect when your spark plugs will fail, and just how much use you’ll get out of them.

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

P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed Related Trouble Codes: P2441: EVAP Vent Valve Stuck Open EVAP trouble...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
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: Have to crank the engine a few times to get it to start.

Engine temperature can significantly affect vehicle components - especially electronics. An engine that won't start when hot usually indicates a problem in one of the vehicle's many circuits. Heat can cause thermal expansion and contraction, as well as increased electrical...

Q: Mazda 3 has no spark and won't start

Hi there. It sounds like there could be a fault somewhere in the camshaft position sensor, crankshaft position sensor, or engine computer circuit. Check all fuses and relays and replace as necessary. The computer will not enable spark to...

Q: Fuel pump not working

Hi. A vehicle that cranks normally but doesn't start indicates a problem with fuel or spark delivery. On the other hand, and engine that doesn't cranks at all or cranks slowly indicates a problem with the starting or charging system....