Check the hose clips for tightness and inspect the trunking for any cracks or splits and next every the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best way to locate a leak is to have the engine paperwork and hot and subsequently spray can lighter gas /propane or brake cleaner almost each joint in turn. If the engine rev s occurring you ve found your leak.
Its next 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 outcome in insufficient fuel innate delivered to the engine. Might afterward be worth cleaning out the idle rapidity control motor / valve as these acquire clogged occurring considering carbon and some brake cleaner washed through helps free things off.
taking into account I start the car, the engine surges up in the company of 1200 and 2000 rpm encourage and forth. I misrepresented the IAC and the TPS considering no amend 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 rapidity screw to belittle the rpm and it would preserve for a while. Now, the engine is continually surging to the lessening where I cannot steer it for distress of broken to the drive train. Any experienced solution?