This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and as a result not compensated for and can thin the engine out and can plus permit the engine to rev happening bearing in mind not desired causing rude running. As its a mechanical malfunction it tends not to incline on the deviation open and you can sometimes listen a hissing noise later the engine running.
Its then worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all consequences in insufficient fuel being delivered to the engine. Might with be worth cleaning out the idle rapidity direct motor / valve as these get clogged going on taking into account carbon and some brake cleaner washed through helps free things off.
gone I begin the car, the engine surges taking place between 1200 and 2000 rpm support and forth. I tainted the IAC and the TPS afterward no bend in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to get used to the idle keenness screw to belittle the rpm and it would retain 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?