This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and appropriately not compensated for and can lean the engine out and can furthermore permit the engine to rev up similar to not desired causing rough running. As its a mechanical deformity it tends not to face upon the defect open and you can sometimes listen a hissing noise in imitation of the engine running.
Thanks for your response. I just checked what you mentioned, that I hadn't already checked, except fuel pressure.Let me say you a tiny more practically the trouble history. It currently has a master tech qualified idle let breathe rule valve and tps installed. without distressing anything, the last (used) ecu and my original, would rule in the car without this symptom.
later I begin the car, the engine surges taking place surrounded by 1200 and 2000 rpm support and forth. I changed the IAC and the TPS bearing in mind no alter in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to familiarize the idle enthusiasm screw to belittle the rpm and it would support for a while. Now, the engine is all the time surging to the point where I cannot drive it for danger signal of broken to the steer train. Any experienced solution?