This could be an airleak after the airflow meter, any ventilate dragged in here isn t seen by the ECU and correspondingly not compensated for and can thin the engine out and can afterward permit the engine to rev occurring in the manner of not desired causing argumentative running. As its a mechanical deviation it tends not to slope on the aberration lively and you can sometimes listen a hissing noise behind the engine running.
Its afterward worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a not at your best pump will every outcome in insufficient fuel innate delivered to the engine. Might furthermore be worth cleaning out the idle zeal govern motor / valve as these acquire clogged happening once carbon and some brake cleaner washed through helps clear things off.
behind I begin the car, the engine surges up between 1200 and 2000 rpm support and forth. I tainted the IAC and the TPS when no change in symptoms. I have noticed that several Lexus SC's have this similar issue. Prior to this I would have to adapt the idle rapidity screw to belittle the rpm and it would keep for a while. Now, the engine is for ever and a day surging to the lessening where I cannot drive it for clock radio of broken to the drive train. Any experienced solution?