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EM-24 < ON-VEHICLE MAINTENANCE > [VQ40DE] COMPRESSION PRESSURE • If the compression pressure is below the minimum value, check the valve clearances and parts associ- ated with the combustion chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head, cylinder head gasket). After checking, measure the compression pressure again. • If some cylinders have low compression pressure, pour a small amount of engine oil into the spark plug hole of the cylinder to re-check it for compression. • If the added engine oil improves the compression, piston rings may be worn out or damaged. Check the piston rings and replace if necessary. • If the compression pressure remains at low level despite the addition of engine oil, the valves may be malfunctioning. Check the valves for damage. Replace the valve or valve seat accordingly. • If two adjacent cylinders have respectively low compression pressure and their compression remains low even after the addition of engine oil, cylinder head gaskets may be leaking, or a valve in adjacent cylinders may be damaged. Inspect and repair as required. 9. Install the components in the reverse order of removal. . 2010 Pathfinder |