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HOMESERVICE MANUALSACURA20043.5RLREPAIR AND DIAGNOSISENGINE PERFORMANCETHEORY AND OPERATIONENGINE CONTROLS - THEORY & OPERATIONVARIABLE VALVE TIMING & LIFT ELECTRONIC CONTROL SYSTEMMDX, RSX, 3.2CL & 3.2TL
2004 Acura 3.5RL

MDX, RSX, 3.2CL & 3.2TL

2004 Acura 3.5RLSECTION MDX, RSX, 3.2CL & 3.2TL
NOTE: On all models except RSX with K20A2 engine, Variable Valve Timing & Lift Electronic Control System (VTEC) rocker arms are used only for intake valves. On RSX with K20A2 engine, both intake and exhaust camshafts are used.

VTEC uses 3 different camshaft lobes and rocker arms, synchronizer pistons, and a VTEC solenoid valve. See Fig 1-Fig 3 . The 2 low lift cam lobes operate primary and secondary (outer) rocker arms. The high lift cam lobe operates the connecting (middle) rocker arm. The PCM controls VTEC solenoid valve which in turn operates synchronizer pistons.

At low speed, primary and secondary rocker arms control valve timing, lift and duration. The connecting (middle) rocker arm remains disengaged, and has no effect on engine operation. At high RPM with heavy engine load, PCM activates VTEC solenoid valve to apply oil pressure to synchronizer pistons located in primary and secondary rocker arms. This locks primary, connecting, and secondary rocker arms together so they are driven as a single unit by high lift cam lobe on which the connecting rocker rides.

RSX has Variable Valve Timing Control (VTC) mechanism on intake camshaft in addition to VTEC system. System improves fuel efficiency and reduces exhaust emissions at all levels of engine speed, vehicle speed, and engine load. VTC system makes continuous intake valve timing changes corresponding to operating conditions. It optimizes intake valve timing to allow engine to produce maximum power. Cam advance is reduced at idle, which stabilizes combustion and reduces engine speed.

Fig 1: Identifying VTEC Rocker Arms & Synchronizer Pistons (MDX, 3.2CL & 3.2TL)
G00070909Courtesy of AMERICAN HONDA MOTOR CO., INC.
RENDER: 1.0x

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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.