4.40
9929422 R02 - 2017-2019 ACE 900 Service Manual
© Copyright Polaris Industries Inc.
EFI DIAGNOSTICS
FUEL SYSTEM TROUBLESHOOTING
The correct position of the throttle body stop screw is
established and set at the factory. DO NOT remove the
tamper proof cap to adjust the throttle body stop screw
or alter its position in any manner. The stop screw
controls the air flow calibration of the throttle body.
FUEL STARVATION / LEAN MIXTURE
Symptoms: Hard start or no start, bog, backfire, popping
through intake / exhaust, hesitation, detonation, low
power, spark plug erosion, engine runs hot, surging, high
idle, idle speed erratic.
• No fuel in tank
• Restricted tank vent, or routed improperly
• Fuel lines or fuel injectors restricted
• Fuel pump inoperative
• Air leak in system
• Intake air leak (throttle shaft, intake boot, gasket or
grommet)
• Failed sensor or disconnected wiring
RICH MIXTURE
Symptoms: Fouls spark plugs, black, sooty exhaust
smoke, rough idle, poor fuel economy, engine runs
rough/ misses, poor performance, bog, engine loads up,
backfire.
• Air intake restricted (inspect intake duct)
• Air filter dirty/plugged
• Poor fuel quality (old fuel)
• Fouled spark plug
• Injector failure
• Failed sensor or disconnected wiring
• Throttle stop screw tampering
POOR IDLE
Symptom: Idle Too High (If greater than 1300 RPM when
engine is warm)
• Throttle stop screw tampering
• Throttle cable sticking, improperly adjusted, routed
incorrectly
• Failed sensor or disconnected wiring
• IAC stuck or inoperative
• Intake air leak
Symptom: Idle Too Low (if less than 1200 RPM when
engine is warm)
• Dirty throttle body (damaged or improper air filter)
• Plugged air filter
• Leaking injector (rich condition)
• Belt dragging
• Throttle stop screw tampering
• Failed sensor or disconnected wiring
Symptom: Erratic Idle
• Throttle cable incorrectly adjusted
• Air Leaks, dirty injector
• TPS damaged or mis-adjusted
• Tight valves
• Belt dragging
• Dirty air cleaner
• Engine worn
• Spark Plug fouled
• Throttle stop screw tampering
• Failed sensor or disconnected wiring
FUEL SYSTEM
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