COMPRESSION PRESSURE
EM-23
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[VQ40DE]
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• 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.
• 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 the checking, measure the compression pressure again.
9. Install the components in the reverse order of removal.
10. Start the engine, and confirm that it runs smoothly.
11. Perform trouble diagnosis. If DTC appears, erase it. Refer to EC-139, "Description"
.
Revision: January 2013 2013 Xterra
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