The IAC is used to maintain the speed of the engine while at idle. It regulates engine speed by precisely adjusting the amount of air allowed into the intake during idle.
A faulty idle air control valve may cause: Erratic idle Engine stall High idle
The throttle body is an essential part of the inlet air stream of a modern gasoline engine. In combination with the electronic throttle control system, the throttle body assembly is designed to control the amount of fresh air entering the engine.
A faulty throttle body could cause: Check engine light Poor fuel economy Engine hesitation Emission standards issues