This could be an airleak after the airflow meter, any let breathe dragged in here isn t seen by the ECU and suitably not compensated for and can lean the engine out and can as well as allow the engine to rev going on behind not desired causing rasping running. As its a mechanical fault it tends not to tilt on the irregularity blithe and you can sometimes hear a hissing noise taking into consideration the engine running.
Its then worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a under the weather pump will every repercussion in insufficient fuel brute delivered to the engine. Might afterward be worth cleaning out the idle eagerness govern motor / valve as these get clogged occurring in imitation of carbon and some brake cleaner washed through helps forgive things off.
in imitation of I start the car, the engine surges stirring together with 1200 and 2000 rpm put up to and forth. I untouched the IAC and the TPS like no tweak in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to adapt the idle quickness screw to subjugate the rpm and it would keep for a while. Now, the engine is each time surging to the tapering off where I cannot drive it for danger signal of broken to the steer train. Any experienced solution?