Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 1256
6E1–100
RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Fuel System Diagnosis
(Cont'd)
Step
No
Yes
Value(s)
Action
10
Locate and repair the loss of vacuum to the fuel
pressure regulator.
Is the action complete?
—
Verify repair
—
11
Replace the fuel pressure regulator.
Is the action complete?
—
Verify repair
—
12
1. Run the fuel pump with the Tech 2.
2. After pressure has built up, turn off the pump and
clamp the supply hose shut with suitable locking
pliers which will not damage the hose.
Does the fuel pressure indicated by the fuel pressure
gauge remain constant?
—
Go to Step 13
Go to Step 15
13
Visually inspect the fuel supply line and repair any
leaks.
Was a problem found?
—
Verify repair
Go to Step 14
14
Remove the fuel tank and inspect for leaky hose or
in–tank fuel line.
Was a problem found?
—
Verify repair
Go to Step 8
15
1. If the pliers are still clamped to the fuel supply hose,
remove the locking pliers.
2. With suitable locking pliers which will not damage
the hose, clamp the fuel return line to prevent fuel
from returning to the fuel tank.
3. Run the fuel pump with the Tech 2.
4. After pressure has built up, remove power to the
pump.
Does the fuel pressure indicated by the fuel pressure
gauge remain constant?
—
Go to Step 11
Go to Step 16
16
Locate and replace any leaking fuel injector(s).
Is the action complete?
—
Verify repair
—
17
Is the fuel pressure indicated by the fuel pressure
gauge above the specified limit?
376 kPa (55
psi)
Go to Step 18
Go to Step 21
18
1. Relieve the fuel pressure. Refer to the Fuel
Pressure Relief.
2. Disconnect the fuel return line from the fuel rail.
3. Attach a length of flexible hose to the fuel rail return
outlet passage.
4. Place the open end of the flexible hose into an
approved gasoline container.
5. Run the fuel pump with the Tech 2.
6. Observe the fuel pressure indicated by the fuel
pressure gauge with the fuel pump running.
Is the fuel pressure within the specified limits?
290–376 kPa
(42–55 psi)
Go to Step 19
Go to Step 20
19
Locate and correct the restriction in the fuel return line.
Is the action complete?
—
Verify repair
—
20
Visually and physically inspect the fuel rail outlet
passages for a restriction.
Was a restriction found?
—
Verify repair
Go to Step 11
6E1–101
RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Fuel System Diagnosis
(Cont'd)
Step
No
Yes
Value(s)
Action
21
Is the fuel pressure indicated by the fuel pressure
gauge above the specified value?
0 kPa (0 psi)
Go to Step 22
Go to Step 23
22
1. Command the fuel pump ON with the Tech 2.
2. Using suitable pliers which will not damage the fuel
hose, gradually apply pressure with the pliers to
pinch the flexible fuel return hose closed.
CAUTION: Do not let the fuel pressure exceed
the second specified value.
Does the fuel pressure indicated by the fuel pressure
gauge rise above the first specified value?
414 kPa (60
psi)
Go to Step 11
Go to Step 7
23
1. Command the fuel pump ON with the Tech 2.
2. Remove the fuel filler cap and listen for the sound of
the fuel pump running.
3. Turn the pump off.
Was the fuel pump running?
—
Go to Step 7
Go to Fuel
System
Electrical Test
Chart
6E1–102
RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
IDLE AIR CONTROL (IAC) SYSTEM CHECK
060R100025
Circuit Description
The powertrain control module (PCM) controls engine
idle speed with the idle air control (IAC) valve. To increase
idle speed, the PCM retracts the IAC valve pintle away
from its seat, allowing more air to bypass the throttle bore.
To decrease idle speed, it extends the IAC valve pintle
towards its seat, reducing bypass air flow. A Tech 2 will
read the PCM commands to the IAC valve in counts.
Higher counts indicate more air bypass (higher idle).
Lower counts indicate less air is allowed to bypass (lower
idle).
Diagnostic Aids
A slow, unstable, or fast idle may be caused by a non–IAC
system problem that cannot be overcome by the IAC
valve. Out of control range IAC Tech 2 counts will be
above 60 if idle is too low, and zero counts if idle is too
high. The following checks should be made to repair a
non–IAC system problem:
D
Vacuum leak (high idle) – If idle is too high, stop the
engine. Fully extend (low) IAC with the IAC motor
analyzer J 39027–A. Start the engine. If idle speed is
above 800 RPM, locate and correct the vacuum leak,
including the PCV system. Check for binding of the
throttle blade or linkage.
D
Lean heated oxygen sensor signal (high air/fuel ratio)
– The idle speed may be too high or too low. Engine
speed may vary up and down, and disconnecting the
IAC valve does not help. Diagnostic trouble codes
P0131, P0151, P0171, or P0174 may be set. Tech 2
oxygen (O2) voltage will be less than 100 mV (0.1 V).
Check for low regulated fuel pressure, water in fuel, or
a restricted injector.
6E1–103
RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
D
Rich heated oxygen sensor signal (low air/fuel ratio) –
The idle speed will be too low. Tech 2 IAC counts will
usually be above 80. The system is obviously rich and
may exhibit black smoke in the exhaust.
D
Tech 2 O2 voltage will be fixed at about 750 mV (0.75
V). Check for high fuel pressure, or a leaking or
sticking injector. A silicon–contaminated heated
oxygen sensor will show an O2 voltage slow to
respond on the Tech 2.
D
Throttle body – Remove the IAC valve and inspect the
bore for foreign material.
D
IAC valve electrical connections – IAC valve
connections should be carefully checked for proper
contact.
D
PCV valve – An incorrect or faulty PCV valve may
result in an incorrect idle speed. Refer to Diagnosis,
Rough Idle, Stalling.
If intermittent poor driveability or idle symptoms are
resolved by disconnecting the IAC, carefully recheck
the connections and valve terminal resistance, or
replace the IAC.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The IAC motor analyzer J 39027–A is used to
extend and retract the IAC valve. Valve movement
is verified by an engine speed change. If no change
in engine speed occurs, the valve can be resettled
when removed from the throttle body.
2. This step checks the quality of the IAC movement in
step 1. Between 700 revolutions per minute (RPM)
and about 1500 RPM, the engine speed should
change smoothly with each flash of the tester light
in both extend and retract. If the IAC valve is
retracted beyond the control range (about 1500
RPM), it may take many flashes to extend the IAC
valve before engine speed will begin to drop. This is
normal on certain engines. Fully extending the IAC
may cause engine stall. This may be normal.
6. Steps 1 and 2 verified the proper IAC valve
operation. This step checks the IAC circuits. Each
lamp on the noid light should flash red and green
while the IAC valve is cycled. While the sequence of
color is not important, if either light is OFF or does
not flash red and green, check the circuits for faults,
beginning with poor terminal contacts.
Idle Air Control (IAC) System Check
Step
Action
Value(s)
Yes
No
1
1. Ignition OFF.
2. Connect the IAC motor analyzer J 39027–A to the
IAC valve.
3. Set the parking brake.
4. Block the wheels.
5. Turn the air conditioning OFF.
6. Idle the engine in Park (A/T) or Neutral (M/T).
7. Install the Tech 2. Display the RPM.
8. Use the IAC motor analyzer J 39027–A to extend
and retract the IAC valve.
9. The engine speed should decrease and increase as
the IAC is cycled.
Does the RPM change?
—
Go to Step 2
Go to Step 3
2
RPM should change smoothly with each flash of the
IAC motor analyzer J 39027–A light.
Does the RPM change within the range specified?
700–1500
RPM
Go to Step 6
Go to Step 3
3
Check the IAC passages.
Are the IAC passages blocked?
—
Go to Step 4
Go to Step 5
4
Clear any obstruction from the IAC passages.
Is the action complete?
—
Verify repair
—
5
Replace the IAC. Refer to On–Vehicle Service, Idle Air
Control Valve.
Is the action complete?
—
Verify repair
—
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