Check the hose clips for tightness and inspect the trunking for any cracks or splits and plus all the vacuum system, the little bore pipes and fittings for cracks and missing parts. The best habit to locate a leak is to have the engine management and hot and later spray lighter gas /propane or brake cleaner re each joint in turn. If the engine rev s occurring 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 tiny more virtually the trouble history. It currently has a master tech approved idle air direct valve and tps installed. without disturbing anything, the last (used) ecu and my original, would manage in the car without this symptom.
behind I begin the car, the engine surges going on in the midst of 1200 and 2000 rpm back up and forth. I tainted the IAC and the TPS in the same way as no bend in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to accustom yourself the idle rapidity screw to humiliate the rpm and it would withhold for a while. Now, the engine is constantly surging to the narrowing where I cannot steer it for alarm bell of broken to the drive train. Any experienced solution?