Seals
Check the valve stem seal (1) and the O-ring (2) (located inside the valve housing) for wear or damage.
Exhaust valve
Remove any combustion residue from the exhaust valve (3) and the valve duct in the cylinder.
Check the valve for wear or damage.
Cylinder gasket
Change the cylinder gasket (4) on assembly.
Solenoid
See 8.11.1 for control unit inspection.