Back-fire

Flames bursting from the exhaust pipe of an Audi rally car

A backfire or afterburn is combustion or an explosion caused by a running internal combustion engine that happens in the exhaust system, rather than inside the combustion chamber. When the flame moves backward it may also be called a "pop-back." A visible flame may shoot out of the exhaust pipe for a short while. A backfire is often a sign that the engine is improperly-tuned.[1]

References

  1. William K. Toboldt; Larry Johnson; W. Scott Gauthier (2006). Automotive Encyclopedia (GOODHEART-WILLCOX AUTOMOTIVE ENCYCLOPEDIA) (18th ed.). ISBN 1590704223.