This could be an airleak after the airflow meter, any freshen dragged in here isn t seen by the ECU and hence not compensated for and can thin the engine out and can moreover permit the engine to rev in the works gone not desired causing coarse running. As its a mechanical anomaly it tends not to face upon the oddity light and you can sometimes listen a hissing noise bearing in mind the engine running.
Its afterward worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a sick pump will all upshot in insufficient fuel inborn delivered to the engine. Might then be worth cleaning out the idle eagerness control motor / valve as these get clogged in the works with carbon and some brake cleaner washed through helps release things off.
taking into account I begin the car, the engine surges in the works amongst 1200 and 2000 rpm support and forth. I misrepresented the IAC and the TPS later than no amend in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to become accustomed the idle promptness screw to subjugate the rpm and it would preserve for a while. Now, the engine is each time surging to the narrowing where I cannot drive it for agitation of damage to the drive train. Any experienced solution?