Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 883
6E–261
3.2L ENGINE DRIVEABILITY AND EMISSIONS
torque may result in poor contact of the seats due to a
loose spark plug. Overtightening may cause the spark
plug shell to be stretched and will result in poor contact
between the seats. In extreme cases, exhaust blow-by
and damage beyond simple gap wear may occur.
Cracked or broken insulators may be the result of
improper installation, damage during spark plug
re-gapping, or heat shock to the insulator material. Upper
insulators can be broken when a poorly fitting tool is used
during installation or removal, when the spark plug is hit
from the outside, or is dropped on a hard surface. Cracks
in the upper insulator may be inside the shell and not
visible. Also, the breakage may not cause problems until
oil or moisture penetrates the crack later.
TS23994
A broken or cracked lower insulator tip (around the center
electrode) may result from damage during re-gapping or
from “heat shock” (spark plug suddenly operating too
hot).
TS23993
D
Damage during re-gapping can happen if the gapping
tool is pushed against the center electrode or the
insulator around it, causing the insulator to crack.
When re-gapping a spark plug, make the adjustment
by bending only the ground side terminal, keeping the
tool clear of other parts.
D
”Heat shock” breakage in the lower insulator tip
generally occurs during several engine operating
conditions (high speeds or heavy loading) and may be
caused by over-advanced timing or low grade fuels.
Heat shock refers to a rapid increase in the tip
temperature that causes the insulator material to
crack.
Spark plugs with less than the recommended amount of
service can sometimes be cleaned and re-gapped , then
returned to service. However, if there is any doubt about
the serviceability of a spark plug, replace it. Spark plugs
with cracked or broken insulators should always be
replaced.
A/C Clutch Diagnosis
A/C Clutch Circuit Operation
A 12-volt signal is supplied to the A/C request input of the
ECM when the A/C is selected through the A/C control
switch.
The A/C compressor clutch relay is controlled through the
ECM. This allows the ECM to modify the idle air control
position prior to the A/C clutch engagement for better idle
quality. If the engine operating conditions are within their
specified calibrated acceptable ranges, the ECM will
enable the A/C compressor relay. This is done by
providing a ground path for the A/C relay coil within the
ECM. When the A/C compressor relay is enabled,
battery voltage is supplied to the compressor clutch coil.
The ECM will enable the A/C compressor clutch
whenever the engine is running and the A/C has been
requested. The ECM will not enable the A/C compressor
clutch if any of the following conditions are met:
D
The throttle is greater than 90%.
D
The engine speed is greater than 6315 RPM.
D
The ECT is greater than 119
°
C (246
°
F).
D
The IAT is less than 5
°
C (41
°
F).
D
The throttle is more than 80% open.
A/C Clutch Circuit Purpose
The A/C compressor operation is controlled by the engine
control module (ECM) for the following reasons:
D
It improvises idle quality during compressor clutch
engagement.
D
It improvises wide open throttle (WOT) performance.
D
It provides A/C compressor protection from operation
with incorrect refrigerant pressures.
The A/C electrical system consists of the following
components:
D
The A/C control head.
D
The A/C refrigerant pressure switches.
D
The A/C compressor clutch.
D
The A/C compressor clutch relay.
D
The ECM.