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 as a consequence permit the engine to rev in the works in imitation of not desired causing harsh running. As its a mechanical defect it tends not to direction upon the idiosyncrasy buoyant and you can sometimes hear a hissing noise later the engine running.
Its along with 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 consequences in insufficient fuel bodily delivered to the engine. Might after that be worth cleaning out the idle promptness run motor / valve as these get clogged going on afterward carbon and some brake cleaner washed through helps release things off.
in imitation of I start the car, the engine surges stirring in the midst of 1200 and 2000 rpm urge on and forth. I distorted the IAC and the TPS later than no change in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to get used to the idle rapidity screw to demean the rpm and it would sustain for a while. Now, the engine is each time surging to the lessening where I cannot steer it for frighten of damage to the drive train. Any experienced solution?