Dashpot System Saab 900 I

DESCRIPTION & OPERATION

A dashpot, located on throttle housing, is used to slow return of throttle valve upon deceleration. This action maintains combustion to reduce emission of unburned HC. Dashpot can be adjusted but not serviced.

TESTING

1. Warm engine to normal operating temperature. Connect tachometer and adjust idle speed to 875 RPM.
2. Raise engine speed to 3000 RPM. Release throttle, noting time between release of throttle and return to 875 RPM. Deceleration time should be 3-6 seconds.

1. Warm engine to normal operating temperature. Check ignition timing and idle speed. Disconnect and plug vacuum hoses to ignition distributor and EGR system.
2. Rotate throttle lever and check that dashpot rod strikes stop at 2400-2600 RPM for non-turbo, 2100-2300 RPM for Turbo models. If rod does not strike stop at specified RPM, adjust dashpot and repeat test.
3. Raise engine speed to 3000 RPM and measure return time to idle. If less than 3 seconds, loosen lock nut and move dashpot closer to throttle stop. If more than 6 seconds, loosen lock nut and move dashpot away from throttle stop.
4. Tighten lock nut. Reconnect vacuum hoses to ignition distributor and EGR system. Repeat deceleration time test.