This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and thus not compensated for and can lean the engine out and can then permit the engine to rev going on subsequent to not desired causing sharp running. As its a mechanical malfunction it tends not to slope upon the idiosyncrasy roomy and you can sometimes hear a hissing noise in imitation of 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 ill pump will every upshot in insufficient fuel being delivered to the engine. Might furthermore be worth cleaning out the idle keenness manage motor / valve as these get clogged up bearing in mind carbon and some brake cleaner washed through helps forgive things off.
taking into account I start the car, the engine surges stirring along with 1200 and 2000 rpm incite and forth. I tainted the IAC and the TPS later no change in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to adjust the idle eagerness screw to lower the rpm and it would hold for a while. Now, the engine is forever surging to the point where I cannot drive it for anxiety of damage to the steer train. Any experienced solution?