Mazda Xedos 6. Handbuch — teil 197

The control unit controls the current through the
coil switching the current on and off with a certain
duty cycle. The current increases as the
duty-cycle increases. The duty cycle varies
between approx. 35% (valve closed) and 85%
(valve opened). Nominal idle speed is obtained
when slightly open.

Three terminal types

The two coils inside this type of idle speed control
valve are connected with the supply voltage using
one common terminal. The other two terminals
lead directly to the control unit. The control unit
switches the current through the solenoid on and
off alternately with a duty cycle between 35 and
85%.

Electrical diagnosis

DYNAMIC TESTS THREE TERMINAL TYPES

STATIC

To perform this measurements the

Remove the idle control valve

relay switching the power to the idle

but leave the electrical

control valve should be closed.

connections in place. Fully

Short circuit the switch in the relay

open or close the rotating

if necessary.

plunger. Switch on the
ignition.

Measurements:

Disconnect the connector and

measure the resistance of the
coil(s). The nominal value is app. 20
ohms.

Check the relay switching the power

result:

Switch on the ignition. The

to the idle control valve

rotating plunger must move

Check the wiring between the relay

to a position equivalent to

and the idle control valve

app. 50% opening, and
remain there.

Check the wiring between the idle
control valve and the control unit
Check the control unit

diagnosis

Mechanical

Check the air chamber on air leakage.

Check engine on air leaks into the intake system.
Remove the idle control valve. The plunger should rotate or move easily.
Clean if necessary.

IGNITION COIL

Function

The ignition coil transforms the battery voltage into the high voltage needed to create a spark.

The ignition coil consists of an electromagnet (the primary coil) and a high voltage coil
(secondary coil).

By switching the current through the primary coil on, a magnetic field is induced. The moment
the current is switched of, the magnetic field suddenly disappears.

This change of magnetic field creates an induction voltage in the secondary coil, high enough to
ionise the mixture. The ionised mixture is a conductor and a current flows through the spark
plug.

Specifications

RESISTANCE:

primary:

± 0,3 - 2 ohms

secondary

± 5k - 20k ohms

supply voltage:

12 V

current limited at:

± 7A

Systems with a distributor

Ignition coils used in combination with a distributor consists of one primary and one
secondary coil.

The high voltage, induced in the secondary coil is connected to one of the spark plugs

selected by the distributor.

Wasted spark ignition coils

The secondary coil has two ends. In a normal ignition coil one of those ends delivers the high
The other end is connected to either the positive (15) or the negative (1) terminal of the prim
In a wasted spark ignition coil both ends are connected to a spark plug. Therefore both spark
will spark at the same time.

wasted spark ignition coil on 2- cylinder 4-stroke engine a wasted spark ignition coil on a 4- cylinder 4-str

To supply the four spark plugs of an 4 cylinder engine, two ignition coils are needed. The pict
below (left) shows an ignition coil for two spark plugs. The ignition coil in the right picture
incorporates two of those. This ignition coil supplies four spark plugs.

Sequential ignition

Sequential ignition systems are distributor less ignition systems using one ignition coil per
cylinder.

Each ignition coil is controlled by the control unit individually.