Difficulty in starting and increased fuel consumption are first alerts; Ignoring the exchange can doom the catalytic converter and cause 'salty' damage
Responsible for the spark that ignites the air-fuel mixture, spark plugs are accurate thermometers of engine health. When worn, they emit clear signals that, if ignored, evolve from simple nuisances to serious mechanical damage. The first warning usually arises at start-up: if the engine revs excessively before starting, especially on cold days, it is likely that the spark plugs will no longer be able to generate the spark necessary for initial combustion.
Part degradation doesn’t just affect starting. Progressive wear of the electrodes or the accumulation of carbon compromise the entire energy efficiency of the vehicle.
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On the move, the symptoms become more evident. The driver may notice an unstable idle speed (the car shakes when stopped at the light) and hesitation in speed resumptions. As the fuel burn becomes inefficient, consumption skyrockets: the engine needs to inject more gasoline or ethanol to compensate for misfiring, drastically reducing autonomy.
The most critical problem, however, is the domino effect. When the spark plug fails, the unburned fuel passes straight into the exhaust system. This can overheat and destroy the catalytic converter — one of the most expensive parts of the vehicle. The dashboard usually warns: a flashing electronic injection light is often the code for misfires in progress.
Visually, condemned candles feature electrodes rounded by erosion, cracked ceramic insulators, or excess black residue. The recommendation is clear: follow the maintenance plan in the owner’s manual and replace the complete set at the first sign of fatigue. The savings on the cheap part almost always result in a high bill in the workshop.
