Check the hose clips for tightness and examine the trunking for any cracks or splits and moreover all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best quirk to locate a leak is to have the engine meting out and warm and then spray lighter gas /propane or brake cleaner just about each joint in turn. If the engine rev s happening 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 not at your best pump will all upshot in insufficient fuel physical delivered to the engine. Might in addition to be worth cleaning out the idle rapidity rule motor / valve as these get clogged occurring bearing in mind carbon and some brake cleaner washed through helps clear things off.
in the manner of I begin the car, the engine surges occurring in the company of 1200 and 2000 rpm back up and forth. I tainted the IAC and the TPS in the manner of no regulate in symptoms. I have noticed that several Lexus SC's have this thesame issue. Prior to this I would have to familiarize the idle eagerness screw to degrade the rpm and it would support for a while. Now, the engine is at all times surging to the narrowing where I cannot drive it for panic of broken to the drive train. Any experienced solution?