EMISSION CONTROL SYSTEMS — Dash Pot (DP) System EC-7 DASH POT (DP) SYSTEM [Diagram showing VTV, Air Filter, and Dash Pot components] Normal Driving Deceleration DP Diaphragm DP Diaphragm VTV VTV EC2134 EC2134 To reduce HC and CO emissions, when decelerating the dash pot opens the throttle valve slightly more than at idle. This causes the air-fuel mixture to burn completely. Condition Diaphragm VTV Throttle Valve Idling Pushed in by return force of CLOSED Idle speed position throttle valve Normal driving Pushed out by diaphragm spring OPEN High speed position Deceleration Pushed in by return force of CLOSED Slightly opens and then slowly closes throttle valve to idle position