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Deceleration device

Deceleration device


The purpose of the deceleration device is to prevent the emission of unburnt hydrocarbons during engine braking. It is incorporated in the IAC valve.

IAC valve

The purpose of the IAC valve is to give:


• smoother engine running

• better cold starting and warming-up performance

• faster idling speed on engagement of the air conditioning system

• compensation for drop in engine speed due to increased load from power steering pump and generator charging, and when driving at high altitudes

• a deceleration function.

The IAC valve controls the flow of air past the throttle valve. The volume of air is determined by the valve's degree of opening, which is governed by signals from the engine management system's control module. The necessary volume of air at any given moment can thus be admitted in order to maintain a constant idling speed.

The IAC valve is a motorized slide valve supplied with power from a PWM output on the engine control module. The valve can move from closed to open position in less than 0.2 seconds. The movement is scarcely visible.