Not an erratic idle like a dirty throttle body gives you. That goes up and down when the AC compressor kicks on, and can send the idle down to 300-400 RPM and stall the engine out. Then it overshoots when the compressor cycles off.
death rattle. a sound produced by a person immediately preceding death, resulting from the passage of air through the mucus in the throat.
Rattlesnake, eastern diamondback rattlesnakeJack Dermidany of 33 species of venomous New World vipers characterized by a segmented rattle at the tip of the tail that produces a buzzing sound when vibrated.