2004 Skidoo ZX Series Service Manual, Page 339Get this manual
Section 07 ENGINES MANAGEMENT (4-TEC) Subsection 01 (OVERVIEW)
OPERATING PRINCIPLE OF ENGINE MANAGEMENT
A highly advanced engine management system (EMS) has been used to ensure high power output with cleanest combustionThe EMS calculates the proper airfuel mixture and ignition timing for each cylinder separatelyThe fuel is injected into the intake port of each cylinderNOTE: On the 1004, the cylinders are referenced as (front) and (rear) instead of PTO and MAG2 1
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52 MM THROTTLE BODY 1Idle bypass valve 2Throttle position sensor (TPS)
FUEL DELIVERY SYSTEM BASIC OPERATION
When the intake valve reaches the correct position, the ECM (engine control module) opens the fuel injector and fuel is discharged into the intake port at the air intake manifold by the high fuel pressure inside the fuel railThe airfuel mixture enters then the combustion chamber through the open intake valveThis mixture is then ignited by the spark plug