1997 Infiniti J30 BaseFACTORY OEM SERVICE PROCEDURE

Mechanical Inspection: Compression

Check engine compression at normal operating temperature at specified cranking speed. Release fuel pressure. See FUEL SYSTEM  . Disconnect crankshaft position sensor harness connector. Remove all spark plugs. Depress accelerator pedal fully to hold throttle valve wide open. See COMPRESSION SPECIFICATIONS  table.

NOTE: If cylinder compression in one or more cylinders is low, repeat inspection using a small amount of oil poured into each cylinder. If compression pressure increases, piston rings may be worn or damaged. If compression pressure does not increase, a valve may be sticking or seating improperly. If compression in any 2 adjacent cylinders is low and does not change after oil is added, there is a leak past head gasket. Make repairs as needed and reinspect.
COMPRESSION SPECIFICATIONS (1)

Application psi (kg/cm2 )
Standard 186 (13.1)
Minimum 142 (10.0)
Maximum Variation Between Cylinders 14 (1.0)
(1) Readings taken at cranking speed (300 RPM).
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.