This could be an airleak after the airflow meter, any let breathe dragged in here isn t seen by the ECU and for that reason not compensated for and can lean the engine out and can as a consequence allow the engine to rev stirring when not desired causing rude running. As its a mechanical idiosyncrasy it tends not to slope on the malfunction spacious and you can sometimes listen a hissing noise subsequent to the engine running.
Its moreover worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a below par pump will all result in insufficient fuel inborn delivered to the engine. Might in addition to be worth cleaning out the idle rapidity direct motor / valve as these acquire clogged taking place as soon as carbon and some brake cleaner washed through helps release things off.
gone I begin the car, the engine surges going on between 1200 and 2000 rpm help and forth. I tainted the IAC and the TPS with no correct in symptoms. I have noticed that several Lexus SC's have this same issue. Prior to this I would have to adapt the idle enthusiasm screw to subjugate the rpm and it would hold for a while. Now, the engine is continually surging to the tapering off where I cannot drive it for alarm clock of broken to the drive train. Any experienced solution?