VESPA GTS Super 125 i.e. Service Station Manual page 134

Injection
Engine stops at idle
ENGINE DOES NOT IDLE/ IDLING IS UNSTABLE/ IDLING TOO LOW
Possible Cause
Presence of faults detected by the self diagnosis
Ignition efficiency
Correctness of the parameters
Intake system cleaning
Intake system sealing (infiltrations)
Fuel system (low pressure)
Engine does not rev down
ENGINE DOES NOT RETURN TO IDLING SPEED/IDLING SPEED TOO HIGH
Possible Cause
Presence of faults detected by the self diagnosis
Ignition efficiency
Correctness of the parameters
Intake system sealing (infiltrations)
Fuel system (low pressure)
Exhaust backfires in deceleration
Possible Cause
Presence of faults detected by the self diagnosis
INJEC - 134
EXHAUST BACKFIRES WHEN DECELERATING
Vespa GTS Super 125 i.e.
Operation
Pump relay
HV coil
Injector
Revolution timing sensor
Air temperature
Coolant temperature
Spark plug
Ignition timing
Throttle valve position sensor
Stepper
Coolant temperature sensor
Intake air temperature sensor
Air filter
Diffuser and throttle valve
Additional air pipe and Stepper
Intake manifold - head
Throttle body - manifold
Intake sleeve
Filter box
Fuel pump
Pressure regulator
Fuel filter
Injector capacity
Operation
Pump relay
HV coil
Injector
Revolution timing sensor
Air temperature
Coolant temperature
Ignition timing
Throttle valve position sensor
Stepper
Coolant temperature sensor
Intake air temperature sensor
Intake manifold - head
Throttle body - manifold
Intake sleeve
Filter box
Fuel pump
Pressure regulator
Fuel filter
Injector capacity
Operation
Pump relay
HV coil
Injector
Revolution timing sensor
Air temperature