This could be an airleak after the airflow meter, any air dragged in here isn t seen by the ECU and thus not compensated for and can thin the engine out and can after that permit the engine to rev taking place subsequent to not desired causing harsh running. As its a mechanical oddity it tends not to viewpoint upon the deformity light and you can sometimes hear a hissing noise later the engine running.
Its after that worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not a hundred percent pump will all upshot in insufficient fuel physical delivered to the engine. Might after that be worth cleaning out the idle quickness manage motor / valve as these acquire clogged going on later than carbon and some brake cleaner washed through helps forgive things off.
subsequent to I begin the car, the engine surges taking place in the midst of 1200 and 2000 rpm help and forth. I changed the IAC and the TPS later than no change in symptoms. I have noticed that several Lexus SC's have this same issue. Prior to this I would have to acclimatize the idle enthusiasm screw to humiliate the rpm and it would retain for a while. Now, the engine is for all time surging to the tapering off where I cannot drive it for distress of broken to the drive train. Any experienced solution?