What are the Symptoms of Bad or Failing Spark Plugs?

The internal combustion engine requires an ignition source to function. Spark plugs provide that ignition sourcing by igniting the air and fuel mix in an engine. This ignition creates an explosion that powers the vehicle and propels it forward. These explosions agitate the pistons that in turn rotate the crankshaft, moving the car forward. Spark plugs create these explosions by creating electrical arcs to uncovered leads, igniting fuel in the engine.


Spark plugs are constructed from durable materials like high-nickel alloys and aluminum oxide ceramic. Despite the durability of spark plugs, they do wear down over time. There are extended-life spark plugs that are manufacturer-specific. These spark plugs have life spans up to 100,000 miles. The most common issue of spark plug failure is the widening of the gap between the two leads. This leads to an efficiency reduction and possible misfiring. Spark plugs can also corrode to the point where they do significant damage to the interior of an engine cylinder. A damaged engine cylinder is costly to repair. You definitely don't want that.


Failing or bad spark plugs have a range of diagnosable symptoms. A common symptom of spark plug issues is slow vehicle acceleration. If you are noticing sluggish acceleration it could be caused by an ailing spark plug. Another indication of poor spark plugs is less than optimal fuel economy. Substandard fuel efficiency can indicate that fuel is not being effectively burned in the combustion cycle. A bad spark plug could also cause misfiring, surging, or hesitating.

Engine misfiring could be caused by a damaged spark plug tip. Engine surging or hesitating could be from the over intake of air into the engine, indicating a potential spark plug issue. Other issues could include a rough idle or difficulty in initial ignition. Both of these issues could be indicative of worn spark plugs going bad or failing. If you are having problems starting your vehicle, a great place to start is the spark plugs.

These issues are usually easy to identify and repair. If you have questions or concerns about replacing or diagnosing spark plugs, give our auto repair shop a call today!