2005 Ski-Doo Tundra, Skandic, Expedition Shop Manual, Page 50Get this manual
Section 02 TROUBLESHOOTING GUIDE Subsection 02 (ENGINE (4-TEC))
ENGINE GENERAL
Symptom: ENGINE BACKFIRES1Check spark plug- Carbon accumulation caused by defective spark plugClean carbon accumulation and replace spark plug2Check fault codes in B.U.D.Ssystem- Check if electrical actuator(s) isare defectiveReplace defective part(s) (refer to COMPONENT INSPECTION AND ADJUSTMENT)3Check leakage on intake manifold- Air leak on intake systemRetighten screws andor replace intake manifold gasket4Check exhaust air leaking- Exhaust gasket is leakingRetighten screws andor replace exhaust gasket5Check intake valve(s) for leaking- Intake valve(s) is(are) leakingRepair or replace valve(s)6Check if fuel supply is sufficient at high RPM- Fuel line is contaminated andor bent (engine gets lean)Clean andor replace defective part(s)