Engine misfire

An engine misfire occurs when the fuel/air mixture in a cylinder fails to ignite.

Table of Contents

• 1. Causes
  • 1.1 Worn Piston Rings
  • 1.2 Faulty Head Gasket
  • 1.3 Improperly Adjusted Valves
  • 1.4 Faulty Spark Plugs
  • 1.5 Faulty Ignition Wiring

Causes

Worn Piston Rings

Worn piston rings can cause a loss of compression in the combustion chamber. As the fuel/air mixture is compressed, the loss of the seal allows some or all of the mixture to leak out.

Faulty Head Gasket

A faulty or damaged head gasket can cause the fuel/air mixture to escape the combustion chamber. It is similar to what happens with worn piston rings, only the leak occurs at the top of the chamber.

Improperly Adjusted Valves

If the intake does not permit the proper amount of fuel and air to enter the combustion chamber, or the exhaust valve does not expel all of the burnt fuel, the proportion of fuel to air may not be correct to ignite.

Faulty Spark Plugs

If the electrode of the spark plug is corroded, or is otherwise incapacitated, there will be no spark for the fuel to ignite.

If the gap is not the correct distance, the charge may not arc.

Faulty Ignition Wiring

If the wiring around the ignition coil is damaged, the charge will not reach the spark plugs and therefore, not ignite the fuel.