An internal combustion engine needs air, fuel and spark to make things happen. When the spark is not there or is less than intended, bad things happen - like stalled vehicles followed by towing and repair bills. Current-generation spark plug technology makes it very easy to forget about them until they go bad and the engine starts to act up.

Our certified technicians at the C&S Subaru in Waterloo routinely replace full sets of spark plugs in vehicles whose owners waited too long to replace old and worn-out plugs. The plugs mostly were worn out for some time, which means the vehicles in which they were installed were wasting fuel and money for thousands of miles.

Typical Service Life of Spark Plugs

Spark plugs generally live and very long and useful service life and come in many types. Some are hotter plugs that easily burn off carbon buildup and typically are installed in engines that rev at higher RPMs and produce lots of power. Because they run at hotter temperatures and in engines that place greater demand on them, the hotter spark plugs often last about half the lifespan of colder spark plugs.

Colder plugs take longer to reach a higher operating temperature and are prone to carbon buildup due to lower operating temperatures. They work well in the majority of engines used in private passenger vehicles. But they need to have the correct gap and be in the correct heat range to deliver optimal performance. When that happens, a typical spark plug could last 30,000 miles or more.

What Makes Spark Plugs Go Bad

Spark plugs seldom go bad right away - unless you drop them or break the insulator while installing them. A properly gapped spark plug that is in the correct heat range for your engine will work flawlessly for many thousands of miles. It only is over tens of thousands of miles of driving that most develop problems that often are caused by other issues.

C & S Subaru

812 Washington St
Directions Waterloo, IA 50702

  • Sales: 319-284-8146
  • Service: 319-284-8145
  • Parts: 319-284-8144

Hours

  • Monday 08:30am - 07:00pm
  • Tuesday 08:30am - 07:00pm
  • Wednesday 08:30am - 07:00pm
  • Thursday 08:30am - 07:00pm
  • Friday 08:30am - 06:00pm
  • Saturday 08:30am - 06:00pm
  • Sunday Closed

An improper gap will accelerate plug deterioration and could burn up the electrode in a relatively short time. That is partly why you should have an experienced technician like ours at the C&S Subaru in Waterloo handle spark plug installation and routine checks.

Carbon buildup on the electrode is what causes most spark plugs to go bad over time. That happens when the plugs do not reach the correct operating temperature to naturally burn off any carbon buildup. Carbon interferes with the electrical flow and weakens the spark.

If the engine is running rich and has too much fuel in the air-fuel mixture, the plugs will foul over time. When pulled, fouled plugs are black and look like they are covered in soot or oil. If an engine is running lean with too much air in the combustion chamber, the plugs could become coated with a chalky white substance that also interferes with the spark.

Signs Your Engine Needs New Spark Plugs

It is their reliable nature that makes it so easy to overlook spark plugs and the rest of the ignition system. Modern engines mostly have onboard computers that can make minor adjustments to timing and fuel delivery that make up for any deterioration in spark plugs and ignition performance. That can make it harder to notice when spark plugs have gone bad. For many vehicle owners, the first sign is a subtle one that  reveals itself in higher fill-up costs due to reduced fuel economy.

If the conditions persists, you likely will notice less power from the engine. In really bad situations, the engine could stumble, hesitate and run poorly. Starting can be difficult, and you might wind up with a failed emissions test when it is time to renew the registration.

Spark Plug Wires Need Attention, Too

While a good set of properly installed spark plugs will help your engine to run its best, it also needs good spark plug wires to ensure the plugs get plenty of power. The wires help to prevent loss of power from the distributor to the plugs. Over time, the insulation and rubbing casing can dry out, crack and transfer less power to the plugs.

If you drive in a hot and dry climate or in an area that gets lots of wintery weather and springtime rainstorms, then the spark plug wires could deteriorate more rapidly. A good set of current-production spark plug wires generally can last about 30,000 miles, but they can wear out sooner depending on the general climate where you live and how often you drive.

When spark plugs outlast the wires that send them the power, then your vehicle will act like it has bad spark plugs. IF the plugs go underpowered for an extended period, they will go bad faster. So it always helps to ensure the wire as well as the plugs are in top condition.