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 as a consequence permit the engine to rev in the works behind not desired causing harsh running. As its a mechanical irregularity it tends not to perspective upon the irregularity fresh and you can sometimes hear a hissing noise like the engine running.
Its furthermore 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 every outcome in insufficient fuel brute delivered to the engine. Might with be worth cleaning out the idle rapidity direct motor / valve as these get clogged up afterward carbon and some brake cleaner washed through helps pardon things off.
in imitation of I begin the car, the engine surges taking place in the midst of 1200 and 2000 rpm support and forth. I untouched the IAC and the TPS later no amend 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 zeal screw to lower the rpm and it would retain for a while. Now, the engine is continuously surging to the lessening where I cannot steer it for scare of damage to the steer train. Any experienced solution?