50000 MI or 80000 KM

Check
    Ignition Timing
Inspect
    Throttle Position Sensor
    Positive Crankcase Ventilation
      If the vehicle is driven in high dust areas than the PCV system should be inspected more often.
    Exhaust Gas Recirculation
    Evaporative Emissions System
Replace
    Oxygen Sensor
    Ignition Cable
    Evaporative Emission Control Canister