Theory Of Operation

WARNING: This page is about a different variant/trim than selected.

MultiAir is an electronically controlled variable intake valve phase and lift system. Unlike conventional intake valve phase and lift system which controls all the cylinder intake valves simultaneously and in the same proportion; MultiAir, through the use of an electronically controlled " hydraulic link" between the camshaft and intake valve, allow for each intake valve to be controlled independently. The valve lift and timing can be adjusted infinitely

The MultiAir valve train has a mechanical camshaft lobe acting on a hydraulic pump located between the camshaft intake lobe and the intake valve. The pump provides oil under pressure to a two-way electro-hydraulic solenoid valve called the Variable Valve Actuator (VVA) Solenoid. The VVA Solenoid is electronically controlled during the specific intake cam lobe event by the Powertrain Control Module (PCM). During the event the VVA Solenoid is commanded to either hold oil pressure or bleed oil. The Variable Valve Actuator (VVA) Solenoid is a normally open solenoid. Both the supply voltage (approximately 8.0 volts) and ground circuit to close the solenoid are provided by the PCM. The position of the VVA Solenoid determines the intake valve timing and lift. This change on valve action is similar to creating a change in the camshaft lobe profile affecting lift and duration of the valve opening.

The VVA high oil pressure absent monitor confirms proper operation of the intake valves by measuring overall intake manifold pressure, monitoring intake manifold pressure pulsations, and monitoring RPM fluctuations during engine cranking. The PCM compares the manifold pressure value, manifold pressure pulsations, and RPM fluctuations to threshold values. The basis of the monitor is that a lack of oil in the high pressure chamber of the solenoid valves will prevent the intake valves from opening. When this occurs, no air is brought into the cylinder during the intake stroke, and so there is no air to compress on the compression stroke. This will result in a lack of vacuum in the manifold, causing prevention of normal RPM and manifold pressure fluctuations that occur during compression and intake events. This condition can be diagnosed by an overall lack of manifold vacuum, a lack of intake manifold pressure pulsations, and a lack of RPM fluctuations during engine cranking. This monitor is enabled during cold starts when there are no active MAP Sensor circuit faults