Ignition System; General; Outline Of Change; General Information - Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement

16-10

IGNITION SYSTEM

GENERAL

OUTLINE OF CHANGES
The following service procedures have been established to correspond to the addition of vehicles with
4G63-MPI engine. Items other than those given below are the same as for the 4G6-GDI engine mounted
in the SPACE WAGON.

GENERAL INFORMATION

This system is equipped with two ignition coils (A
and B) with built-in power transistors for the No.
1 and No. 4 cylinders and the No. 2 and No. 3
cylinders respectively.
Interruption of the primary current flowing in the
primary side of ignition coil A generates a high
voltage in the secondary side of ignition coil A.
The high voltage thus generated is applied to the
spark plugs of No. 1 and No. 4 cylinders to generate
sparks. At the time that the sparks are generated
at both spark plugs, if one cylinder is at the
compression stroke, the other cylinder is at the
exhaust stroke, so that ignition of the compressed
air/fuel mixture occurs only for the cylinder which
is at the compression stroke.
In the same way, when the primary current flowing
in ignition coil B is interrupted, the high voltage
thus generated is applied to the spark plugs of
No. 2 and No. 3 cylinders.
The engine-ECU <M/T> and engine-A/T-ECU
<A/T> turns the two power transistors.
SYSTEM DIAGRAM
Air flow sensor
Barometric pressure
sensor
Intake air temperature
sensor
Engine coolant
temperature sensor
Idle position switch
Camshaft position sensor
Crank angle sensor
Ignition switch-ST
Detonation sensor
Vehicle speed sensor
Inhibitor switch <A/T>
ENGINE ELECTRICAL -
Engine-ECU
<M/T> and
Engine-A/T-
ECU <A/T>
Cylinder No.
To tachometer
Ignition System
Inside the ignition coils alternately on and off. This
causes the primary currents in the ignition coils
to be alternately interrupted and allowed to flow
to fire the cylinders in the order 1-3-4-2.
The engine-ECU <M/T> and engine-A/T-ECU
<A/T> determines which ignition coil should be
controlled by means of the signals from the
camshaft position sensor which is incorporated in
the camshaft and from the crank angle sensor which
is incorporated in the crankshaft. It also detects
the crankshaft position in order to provide ignition
at the most appropriate timing in response to the
engine operation conditions. It also detects the
crankshaft position in order to provide ignition at
the most appropriate timing in response to the
engine operation conditions.
When the engine is cold or operated at high
altitudes, the ignition timing is slightly advanced
to provide optimum performance.
Furthermore, if knockking occurs, the ignition timing
is gradually retarded until knocking ceases.
Ignition switch
Ignition
coil A
Spark plug
4 1
Battery
Ignition
coil B
2 3