Check the hose clips for tightness and inspect the trunking for any cracks or splits and in addition to all the vacuum system, the small bore pipes and fittings for cracks and missing parts. The best artifice to locate a leak is to have the engine dispensation and warm and later spray lighter gas /propane or brake cleaner all but each joint in turn. If the engine rev s stirring you ve found your leak.
Thanks for your response. I just checked what you mentioned, that I hadn't already checked, except fuel pressure.Let me tell you a little more not quite the burden history. It currently has a master tech approved idle freshen direct valve and tps installed. without upsetting anything, the last (used) ecu and my original, would run in the car without this symptom.
behind I start the car, the engine surges stirring in the company of 1200 and 2000 rpm put up to and forth. I misrepresented the IAC and the TPS taking into consideration no regulate 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 enthusiasm screw to demean the rpm and it would retain for a while. Now, the engine is for eternity surging to the dwindling where I cannot steer it for agitation of damage to the steer train. Any experienced solution?