This could be an airleak after the airflow meter, any freshen dragged in here isn t seen by the ECU and appropriately not compensated for and can thin the engine out and can as a consequence permit the engine to rev going on once not desired causing rough running. As its a mechanical irregularity it tends not to tilt upon the deviation lively and you can sometimes listen a hissing noise in the same way as the engine running.
Thanks for your response. I just checked what you mentioned, that I hadn't already checked, except fuel pressure.Let me tell you a little more about the pain history. It currently has a master tech approved idle air direct valve and tps installed. without moving anything, the last (used) ecu and my original, would run in the car without this symptom.
next I start the car, the engine surges occurring amid 1200 and 2000 rpm urge on and forth. I misused the IAC and the TPS subsequently no correct in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to accustom yourself the idle readiness screw to demean the rpm and it would preserve for a while. Now, the engine is until the end of time surging to the narrowing where I cannot drive it for dread of broken to the steer train. Any experienced solution?