Chrysler laser 1990 Technical Information Manual page 157

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IDLE SPEED CONTROL SERVO
Extend
The idle speed control servo, consisting of a step
type motor and pintle, is mounted on the throttle
body. As the motor operates, the pintie extends or
retracts to control the bypass air flow.
The step type motor, or stepper motor, is a motor
that rotates a fixed angle when an electric Pulse is
The rotor of the stepper motor used here rotates 15
FUEL SYSTEM - Idle Speed Control
Throttle bodv
Magnet rotor
Stepper motor
degrees whenever a pulse is applied.
The pintle meshes with the lead screw on the
magnet rotor shaft, as shown in the above illustra-
tion. When the rotor rotates in the direction of the
outlined arrow, the lead screw causes the pintle t0
retract towards the interior of the motor. When the
rotor rotates in the direction of the solid arrow, the
pintle extends.