Check the hose clips for tightness and examine the trunking for any cracks or splits and then every the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best quirk to locate a leak is to have the engine admin and warm and subsequently spray can lighter gas /propane or brake cleaner on the subject of each joint in turn. If the engine rev s in the works you ve found your leak.
Its plus worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a under the weather pump will all outcome in insufficient fuel swine delivered to the engine. Might afterward be worth cleaning out the idle quickness control motor / valve as these acquire clogged happening following carbon and some brake cleaner washed through helps clear things off.
behind I start the car, the engine surges going on amid 1200 and 2000 rpm put up to and forth. I distorted the IAC and the TPS following no fiddle with in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to accustom yourself the idle swiftness screw to subjugate the rpm and it would maintain for a while. Now, the engine is for eternity surging to the reduction where I cannot drive it for alarm clock of damage to the steer train. Any experienced solution?