The VVT system constantly adjusts intake valve timing based upon operating conditions. The ECM system controls the Oil Control Valve (OCV) with a variable duty cycle. The Oil Control Valve then supplies oil to the advance or retard side of the VVT Controller. The oil applied to the VVT Controller will cause the intake cam to advance or retard depending on the position of the Oil Control Valve. The ECM verifies that the desired camshaft angle has been achieved by monitoring the camshaft position sensor. If anything has happened to the camshaft position sensor or if a timing belt has been on this car recently there could be issues with the wiring going to the sensor or the timing belt. If these factors can be ruled out then you're probably looking at the VVT controller sticking or binding not returning back on a retarded or advanced signal. The actual duty cycle solenoids or oil control valves could also be plugged up or the filter screen behind them can be restricted. You could possibly pull the OCV and check these nylon screens. This would explain the rough idle or misfire situation. Given the high miles there probably is a good chance the VVT I controller on the camshaft is worn out or sticking.
December, 12, 2010 AT 11:32 PM
Where is the VVT 1 controller, the duty cycle solenoids and oil control valves located?
February, 23, 2011 AT 10:54 PM
VARIABLE VALVE TIMING (VVT) CONTROL SYSTEM
VVT system controls the intake valve timing to proper timing in response to driving condition. ECM controls OCV (Oil Control Valve) to make the intake valve timing properly, and, oil pressure controlled with OCV is supplied to the VVT controller, and then, VVT controller changes relative position between the camshaft and the crankshaft.
VARIABLE VALVE TIMING (VVT) SENSOR
VVT sensor (VV1 or VV2 signal) consist of a signal plate and pickup coil.
The VV1 or VV2 signal plate has 1 tooth on its outer circumference and is mounted on the intake camshafts.
When the camshafts rotate, the protrusion on the signal plate and the air gap on the pickup coil change, causing fluctuations in the magnetic field and generating an electromotive force in the pickup coil. The actual camshaft angle is detected by the VVT sensor and it provides feedback to the ECM to control the intake valve timing in response to during condition.