1. Verify that the joint shaft is not twisted or cracked.
2. Turn the joint shaft by hand and verify that the bearing rotates smoothly and freely.

Drive shaft
Joint shaft removal/installationMazda 6 Service Manual: Variable valve timing actuator removal/installation
L3
Caution
Variable valve timing actuator can not be disassembled because it
is a precision unit.
Note
Variable valve timing actuator camshaft sprocket is integrated
with the variable valve timing actuator and cannot be disassembled.
1. Follow the timing chain removal/installati ...
Mazda 6 Service Manual: Pcv valve inspection
1. Disconnect the negative battery cable.
2. Remove the intake maniforld.(see INTAKE-AIR SYSTEM REMOVAL/INSTALLATION.)
3. Remove the PCV valve.
4. Blow through the valve and verify that air flows as specified.
If not as specified, replace the PCV valve.
Specification
...