throw a monkey wrench v. phr.,
informal To cause something that is going smoothly to stop.
The game was going smoothly until you threw a monkey wrench into the works by fussing about the rules. The Michigan tacklers threw a wrench into the Wisconsin team's offense. He hoped to see the class plan fail and looked for a chance to throw a wrench in the machinery. [TahlilGaran] English Idioms Dictionary ▲