Fiat 1998 Marea Weekend, Service Manual

Page: 304 / 846

Engine
Fuel system
16v
Marea- Marea Weekend 9
99 update
ENGINE IDLE SPEED
ADJUSTMENT ACTUATOR
The actuator, fitted on the butterfly casing, in-
tercepts a flow of air which, taken from up-
stream of the butterfly, returns it downstream:
it has the task of guaranteeing the additional
air for the engine with the butterfly closed in
all conditions where it is required (idling, de-
celeration).
A stepping motor is used to achieve the latter
and it is fixed to the butterfly casing and oper-
ated by a circuit inside the engine management
control unit.
Operating principle
The actuator consists of:
- an electric stepping motor which has two windings in the stator and a rotor which includes a certain
number of pairs of permanent magnet poles;
- a screw-female screw type reduction gear which transforms the rotary motion into rectilinear motion.
The stepping motor is operated by the engine management control unit which, combining the offset and
the direction in which the current flows through the windings, causes the rotor to rotate in both directions
through a given number of steps.
The screw-female screw coupling causes the movement of stem, fitted with a tapered shutter, which varies
the passage of the by-pass duct and, as a result, the quantity of air drawn in by the engine to obtain the
desired speed even when external loads are applied (air conditioning, fans, power assisted steering, etc.).
39A 37A
40A
38A
Wiring connector
34
Print n° 506.763/15