2012 Acura MDXFACTORY OEM SERVICE PROCEDURE

VTEC System

  • The VTEC system changes the cam profile to correspond to engine speed. It maximizes torque at low engine speed and output at high engine speed. The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.
  • The intake valve side has primary and secondary rocker arms. These rocker arms are locked and separated to change the cam profile by switching the oil passages. Roller rockers are used to minimize mechanical friction.
    Fig 1: Identifying Intake Valve Side Primary And Secondary Rocker Arms
    G08052474Courtesy of AMERICAN HONDA MOTOR CO., INC.
  • The VTEC system oil pressure is switched by the rocker arm oil control valve changing the hydraulic circuit. The rocker arm oil control valve is controlled by the rocker arm oil control solenoid. The rocker arm oil pressure switch detects VTEC system oil pressure and sends this information to the PCM.
    ENGINE SPEED ROCKER ARM OIL CONTROL SOLENOID INTAKE VALVE LIFT
    LOW OFF LOW
    HIGH ON HIGH
Factory Service Tools

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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.

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