This could be an airleak after the airflow meter, any air dragged in here isn t seen by the ECU and fittingly not compensated for and can thin the engine out and can then permit the engine to rev in the works subsequent to not desired causing prickly running. As its a mechanical irregularity it tends not to aim on the irregularity well-ventilated and you can sometimes listen a hissing noise in the same way as the engine running.
Its plus worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not at your best pump will all result in insufficient fuel subconscious delivered to the engine. Might then be worth cleaning out the idle zeal govern motor / valve as these get clogged up past carbon and some brake cleaner washed through helps pardon things off.
past I start the car, the engine surges in the works amongst 1200 and 2000 rpm back up and forth. I changed the IAC and the TPS taking into consideration no modify in symptoms. I have noticed that several Lexus SC's have this same issue. Prior to this I would have to get used to the idle rapidity screw to demean the rpm and it would keep for a while. Now, the engine is continually surging to the reduction where I cannot drive it for danger signal of broken to the drive train. Any experienced solution?