Lexus Troubleshooting Questions? Ask a Lexus Expert
How many miles are on this vehicle? Are you a private owner or shop? Has there been any recent work done to the timing belt or has the front valve cover then off to check for sludge?
205,000 miles... no front valve cover checked for sludge. I had the oil cleaned/flushed in 9/09. Tues I put 2/3 pint of seafoam into oil and 1/3 into gas. check engine went off, ran fine. Wed check engine light on again and same symptoms. Had oil and filter changed and now car runs fine and check engine light is off again.
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.