back·fire 
(băkfīr′)
(băkfīr′)n.
1. An explosion of prematurely ignited fuel or of unburned exhaust gases in an internal-combustion engine.
2. The backward escape of gases or cartridge fragments when a gun is fired.
3. A fire started in the path of an oncoming fire in order to deprive it of fuel and thereby control or extinguish it.
intr.v. back·fired, back·fir·ing, back·fires
1. To explode in the manner of or make the sound of a backfire.
2. To start or use a backfire in extinguishing or controlling a forest fire.
3. To produce an unexpected, undesired result.