3-50 ENGINE CONTROL SYSTEM
CHART13: UNSTABLE IDLING/TROLLING (OR ENGINE TENDS TO STALL)
Before starting this troubleshooting, make sure that:
• There is no self-diagnostic code indication.
START
< Ignition switch “ON” >
Check “5” terminal voltage.
Is result OK? (See page 3-38.)
YES
< Ignition switch “ON” >
Check “24” terminal voltage.
Is result OK? (See page 3-38.)
YES
< Individual check >
Check neutral switch function.
Is result OK?
NO
YES
NO (Always 0 V)
Neutral switch failure
ECM failure
(Always 5 V)
[
NOTE1
]
YES
< Individual check >
Check CTP switch function.
Is result OK? (See page 3-43.)
NO
CTP switch failure
[
NOTE2
]
Possible cause:
• Incorrect by-pass air screw adjustment
[
NOTE3
]
• IAC valve failure
[
NOTE3
]
• IAC passage failure (clogged hose, etc.)
[
NOTE3
]
• Spark plug failure
• Ignition coil failure
• ECM failure
• Wire continuity/connection failure
• Failure of high pressure fuel system components:
- Fuel injector (clog, stuck valve, etc.)
- Fuel pressure regulator (incorrect regulated pressure, etc.)
- Fuel pump (clogged suction filter, leakage in tank, etc.)
- Fuel filter (clog, etc.)
- Hose (clog, kink, leakage, etc.)
NOTE1:
If the neutral switch has failed (while engine running), the engine will tend to stall when shifting into gear.
If the neutral switch has failed as “always ON”, the engine speed is limited to 3000 r/min by intermittent fuel
injection and ignition timing is fixed at BTDC 9°.
If the neutral switch has failed as “always OFF”, the engine can not cranked.
NOTE2:
If the CTP switch has failed, the engine will tend to stall when decelerating.
NOTE3:
•
The self-diagnostic code “3-1” may not be indicated because the IAC valve condition depends on the ECM
control. (See the page 3-29.)
•
If the IAC valve has failed, “Fast-idle function (warm-up mode)” won’t operate.
NO (Always 0 V)
(Always 5 V)
