B350 1 Ton Van V8-318 5.2L VIN Y FI (1988)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
The AIS motor is operated by the SMEC and controls engine idle speed by controlling air flow through the throttle body by-pass channel. The SMEC
computes proper idle speed based in signals from vehicle and engine sensors and the switch inputs, and transmits voltage signals to the AIS motor to
open or close the by-pass channel in order to maintain the proper engine speed.
Basic, no-load idle speed is determined by the amount of air flowing through the throttle body past the closed throttle plate. The AIS motor alters idle
speed by allowing increased air flow through the by-pass channel; increasing idle speed when the channel is opened and decreasing idle speed when the
channel is closed. In addition, the AIS motor is signaled to open the by-pass channel during deceleration to prevent stalling and mixture enrichment
caused by sudden closing of the throttle plate.
