This could be an airleak after the airflow meter, any expose dragged in here isn t seen by the ECU and appropriately not compensated for and can lean the engine out and can as well as 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 viewpoint on the malformation vivacious and you can sometimes hear a hissing noise like the engine running.
Its moreover worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a below par pump will all repercussion in insufficient fuel creature delivered to the engine. Might furthermore be worth cleaning out the idle enthusiasm run motor / valve as these get clogged in the works subsequently carbon and some brake cleaner washed through helps clear things off.
similar to I begin the car, the engine surges going on amongst 1200 and 2000 rpm assist and forth. I distorted the IAC and the TPS with no correct in symptoms. I have noticed that several Lexus SC's have this same issue. Prior to this I would have to acclimatize the idle readiness screw to lower the rpm and it would hold for a while. Now, the engine is constantly surging to the point where I cannot steer it for dread of broken to the steer train. Any experienced solution?