What Causes Spark Plugs to Wear Out? | YourMechanic Advice

What Causes Spark Plugs to Wear Out?

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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.


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Michael

15 years of experience
574 reviews
Michael
15 years of experience
Hyundai Accent - Spark Plugs - Marietta, Georgia
I had a great experience with Michael. He's extremely professional, friendly, and understands his craft. Highly recommended.
Honda CR-V - Spark Plug Replacement - Alpharetta, Georgia
Second time Michael has serviced one of our Hondas. On time, efficient, knowledgeable. We'll not only use again but recommend him / your service to others.

Chris

15 years of experience
274 reviews
Chris
15 years of experience
Dodge Durango - Spark Plugs - San Diego, California
Showed up early, was a friendly dude, kept me informed via text, did clean work and finished early. Would hire again.
Volkswagen Jetta - Spark Plugs - San Diego, California
Very pleased with the work done. Chris was on time and the work was done within the time stated. Chris was very professional and pleasant. For any additional work on my Jetta I will make sure to ask for Chris.

Larry

15 years of experience
15 reviews
Larry
15 years of experience
Chevrolet Cruze - Spark Plugs - Oak Forest, Illinois
Fantastic job. Arrived early, took his time and was fantastic. Personable and explained everything. Top notch for sure.
Dodge Avenger - Spark Plugs - Chicago Heights, Illinois
Mechanic arrived early and completed work within half an hour. I am very pleased and would highly recommend.

Joseph

19 years of experience
507 reviews
Joseph
19 years of experience
Subaru Outback - Spark Plugs - Sandy, Utah
Joseph did an outstanding job. He finished ahead of schedule, explained what he had done, and advised what to expect from my old car down the road. Joseph knows his profession and shares his knowledge about your vehicle. I have already recommended him to my co-workers.
Honda Crosstour - Spark Plugs - Salt Lake City, Utah
Helpful, friendly and timely. Goes above and beyond to make sure you’re good to go and answers any questions. Can’t say enough good things and quality of work is top notch! Already booked again. Thanks!

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