I recently purchased a 2005 Lexus 430 SC with 36,000. During normal idling the engine will turn off. This has happened several times and there seems to be no pattern. I have taken the car the service department of an excellent Lexus dealer in Redwood City, CA. The service people performed a full service and I was told that no error code showed up on the computer diagnostics. I use premium gas. The service department was not able to get the engine to stall while they were servicing it. HELP!