Backfiring Basics

• Backfiring in an automobile is related to a problem in the emission system of the engine. Several factors can cause an improper ratio of fuel to air, such as a clogged fuel filter. When the ratio of fuel to air is incorrect, fuel remains unburned in the exhaust manifold and can ignite unpredictably. This ignition (explosion) of unburned fuel results in the loud popping noise recognized as a backfire.
  
  

Timing Issues

• The intake valve in an automobile has to open and close at the correct time in order for backfiring not to occur. If the timing of the engine is such that the spark plugs fire prior to the close of the intake valve (this is caused by improper wiring in the ignition), then the flame front ignites the fuel in the intake manifold and a backfire occurs.
  
  

Catalytic Converters

• Catalytic converters in an car regulate the emissions the vehicle produces. When a catalytic converter is damaged or missing, it is more difficult to regulate and to convert chemicals before they leave the exhaust system. If the chemicals are less regulated, there is a greater chance that they will build up and ignite in a backfire because the converter cannot dispose of the excess.
  
  

Fuel Filters and Pumps

• Fuel filters filter out dirt and other contaminants from the fuel before they enter the fuel system. Fuel pumps feed fuel from the tank to the engine. If the fuel filter is clogged, then the pump is damaged. If the pump is damaged, then the ratio of fuel to air becomes incorrect. The improper ratio causes unburned fuel to ignite (the backfire).
  
  

More Information

• Because backfiring can be related to many parts of the emission system, car owners should familiarize themselves with each part of the system and the function they serve.