Isuzu 4JA1 Workshop Manual page 388

6E-134 Engine Control System (4JH1)
Step
4 1. Turn OFF the ignition.
2. Inspect for the following conditions:
•
An EGR valve control vacuum hose is
damaged or kinked.
•
EGR solenoid valve vacuum hoses are
damaged or kinked.
•
EGR solenoid valve ventilation is damaged.
•
An EGR valve is stuck open.
•
Any type of restriction in the exhaust
system.
•
Air leakage around the MAF sensor or
debris in the sensor housing.
•
Air leaking around any of the air induction
tubing between the MAF sensor and intake
manifold.
•
Turbine
turbocharger shaft spinning speeds. Refer
to the Turbocharger in Engine Mechanical
section for diagnosis.
•
Restricted air cleaner element, restricted or
collapsed air tubing between the air cleaner
and the turbocharger.
•
Oil in the air tubing causing an incorrect
MAF sensor
adhesion of oil, inside of the tubing,
intercooler and turbocharger needs to be
wipe off.
•
Contaminated,
sensor.
3. Repair or replace as necessary.
Did you find and correct the condition?
5 1. Turn OFF the ignition.
2. Disconnect the EGR valve control vacuum hose
from the EGR valve.
3. Connect a hand-held vacuum pump (5-8840-
0279-0/J-23738-A) to the disconnected vacuum
hose.
4. Start the engine and let engine idle.
5. Perform the EGR Solenoid Valve test with the
scan tool.
6. Command the EGR Solenoid Valve ON and OFF
with the scan tool.
Does the hand-held vacuum pump indicate more
than 50 cmHg (20 inHg) when commanding the ON
and less than 10 cmHg (4 inHg) when commanding
OFF?
6 1. Turn OFF the ignition.
2. Disconnect the hand-held vacuum pump from the
vacuum hose.
3. Connect the hand-held vacuum pump to the
vacuum port of EGR valve.
4. Start the engine and let engine idle.
5. Apply vacuum pressure to the EGR valve while
observing the MAF Sensor parameter.
Does the MAF Sensor parameter decrease by at
least 200 mg/strk when the vacuum pressure is
applied?
Action
shaft binding causing
signal. When there
skewed or slow
Value(s)

lower
is
MAF

Yes
Go to Step 10 Go to Step 5
Go to Step 6 Go to Step 9
Go to Diagnostic
Aids Go to Step 7
No