This could be an airleak after the airflow meter, any freshen dragged in here isn t seen by the ECU and therefore not compensated for and can thin the engine out and can moreover allow the engine to rev up in the same way as not desired causing harsh running. As its a mechanical malfunction it tends not to twist on the malformation buoyant and you can sometimes hear 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 say you a little more about the trouble history. It currently has a master tech certified idle let breathe direct valve and tps installed. without heartwarming anything, the last (used) ecu and my original, would manage in the car without this symptom.
similar to I begin the car, the engine surges going on amongst 1200 and 2000 rpm back and forth. I distorted the IAC and the TPS later no correct in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to acclimatize the idle speed screw to degrade the rpm and it would hold for a while. Now, the engine is continually surging to the lessening where I cannot drive it for distress signal of broken to the steer train. Any experienced solution?