A spark plug is an important component of any gasoline engine. Its serviceability directly affects the stability of the power unit, the car's appetite, and ease of starting. However, drivers often encounter such a nuisance as a spark plug breakdown. Let's take a detailed look at what this malfunction is and how to recognize it.

The essence of the malfunction

Spark plug breakdown is a defect in which the electric discharge does not go through the central electrode but finds another path — through damage or contamination on the ceramic insulator. As a result, the spark does not occur where it should, and the air-fuel mixture in the cylinder does not ignite. Simply put, a breakdown is the destruction of the insulating layer. Instead of a full spark in the combustion chamber, you get ignition misfires, unstable engine operation, and a noticeable loss of traction.

External signs of breakdown

Often, such a malfunction can be detected with the naked eye. Here are key points to pay attention to in order to understand what a broken spark plug looks like:
  1. Dark stripes on the insulator.
    On the white ceramic surface, a dark "track" is clearly visible — a trace resembling a lightning discharge. This is exactly where the electrical breakdown occurred.
  2. Microcracks in the ceramic.
    Upon careful inspection, barely noticeable cracks can be found. It is through them that the current "leaks," causing malfunctions in the ignition system.
  3. Signs of overheating or erosion.
    At the base of the spark plug, darkening, signs of overheating, or even pinpoint holes on the insulator may be observed. This is a sure sign that the spark plug is broken.
  4. Change in the shape of the spark gap.
    Sometimes, due to a breakdown, the discharge passes not between the electrodes but along the outer side of the spark plug. In this case, burn marks remain on the metal body.
  5. Smell of burning and oil traces.
    With prolonged operation with a broken spark plug, a characteristic burning smell appears, and soot and traces of breakdown can be noticed on the rubber caps of the coils.

Car behavior with a broken spark plug

You can understand that the problem is in the spark plugs without removing them — by how the car behaves. If the spark plug is broken, you will notice:
  • the engine starts to run unevenly, "misfiring";
  • during acceleration, dynamics noticeably drop;
  • fuel consumption increases;
  • jerks and vibration appear when starting;
  • the "Check Engine" indicator lights up on the dashboard.
Often, drivers mistakenly suspect a faulty coil or injector, and only diagnostics show that the broken spark plug is to blame.

Causes of breakdown

  1. Overheating.If the spark plug does not match the engine in heat rating, it overheats, and cracks appear on the insulator.
  2. Poor-quality fuel.Deposits of carbon and soot form a conductive layer on the surface.
  3. Mechanical damage.Careless installation or an impact can lead to the appearance of a microcrack.
  4. Natural wear.Over time, the ceramic loses its strength and can no longer withstand high voltage.

Ways to check a spark plug

  1. Visual inspection.Inspect the spark plug under good lighting. Any crack or dark stripe is a reason for replacement.
  2. Spark test.Remove the high-voltage cap, place the spark plug against the "ground," and check for a stable spark. If the discharge goes sideways, then the spark plug is broken.
  3. Multimeter test.The resistance of a good spark plug is usually in the range of 4-6 kOhm. A significant deviation from these values indicates damage to the insulation.

What to do if a breakdown is detected

The only effective way to solve the problem is to replace the spark plugs. Repairing them is useless, since cracks on the ceramic insulator cannot be restored. After installing new spark plugs, it is worth checking the condition of the coils and tips — a breakdown sometimes affects them as well.

Prevention of breakdown

  • install spark plugs recommended by the vehicle manufacturer;
  • avoid washing the engine with high-pressure devices;
  • replace spark plugs in a timely manner (approximately every 20-30 thousand km);
  • make sure that oil does not get into the spark plug wells.
Now you understand what a broken spark plug is and what this malfunction looks like. At the first symptoms of unstable engine operation, it is worth unscrewing and carefully inspecting the spark plugs. Replacing these relatively inexpensive parts will help avoid serious damage to the coils, cylinders, and fuel system components.