Suzuki DF150 Service Manual page 138

CHART 20: 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 shift position sensor output voltage
change. (See page 3-60.)
Is result OK?
YES
<Ignition switch "ON">
Check throttle position sensor output
voltage change. (See page 3-59.)
Is result OK?
YES
Possible cause:
• Incorrect by-pass air screw adjustment [NOTE 3]
• IAC valve failure [NOTE 3]
• IAC passage failure (clogged, etc.) [NOTE 3]
• 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.)
NOTE 1
If shift position sensor has failed (while engine running), engine will tend to stall when shifting into gear.
NOTE 2
If throttle position sensor has failed, engine will tend to stall when decelerating.
NOTE 3
• The self-diagnostic code "3-1" may not be indicated because IAC valve condition depends on ECM con-
trol. (See page 3-40.)
• If IAC valve has failed, "Fast-idle function (warm-up mode)" won't operate.
• Shift position sensor failure
NO
[NOTE 1]
• Wire continuity/connection failure
• Throttle position sensor failure
NO
[NOTE 2]
• Wire continuity/connection failure
ENGINE CONTROL SYSTEM 3-79