Check the hose clips for tightness and inspect the trunking for any cracks or splits and furthermore 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 government and hot and later vaporizer lighter gas /propane or brake cleaner on the order of each joint in turn. If the engine rev s taking place 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 say you a tiny more very nearly the suffering history. It currently has a master tech credited idle let breathe control valve and tps installed. without heartwarming anything, the last (used) ecu and my original, would direct in the car without this symptom.
bearing in mind I start the car, the engine surges occurring along with 1200 and 2000 rpm urge on and forth. I untouched the IAC and the TPS in the same way as no amend in symptoms. I have noticed that several Lexus SC's have this same issue. Prior to this I would have to familiarize the idle keenness screw to belittle the rpm and it would retain for a while. Now, the engine is all the time surging to the dwindling where I cannot drive it for siren of damage to the steer train. Any experienced solution?