Check the hose clips for tightness and inspect the trunking for any cracks or splits and after that all the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best artifice to find a leak is to have the engine dealing out and warm and subsequently vaporizer lighter gas /propane or brake cleaner on each joint in turn. If the engine rev s happening you ve found your leak.
Its as well as worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a in poor health pump will all repercussion in insufficient fuel instinctive delivered to the engine. Might after that be worth cleaning out the idle speed control motor / valve as these get clogged occurring in the same way as carbon and some brake cleaner washed through helps release things off.
afterward I begin the car, the engine surges up amid 1200 and 2000 rpm back and forth. I misrepresented the IAC and the TPS like no change in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to familiarize the idle zeal screw to degrade the rpm and it would sustain for a while. Now, the engine is each time surging to the tapering off where I cannot steer it for startle of damage to the steer train. Any experienced solution?