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 lean the engine out and can next allow the engine to rev going on when not desired causing scratchy running. As its a mechanical irregularity it tends not to twist upon the deviation light and you can sometimes listen a hissing noise when the engine running.
I started the car taking place this morning, it starts up and runs at 1750 and within a minute or correspondingly climbs exceeding 2500.. It is direction smooth though, just pretension well ahead than it should be. I afterward checked the throttle screw plate/return screw, purposefully turned it out and nothing changed. put it back up to exactly where it was. No vacuum leak sounds and all links verified. I feel fine nearly them as I've been in there a bunch of times..
taking into account I begin the car, the engine surges taking place together with 1200 and 2000 rpm back up and forth. I changed 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 adjust the idle promptness screw to humiliate the rpm and it would hold for a while. Now, the engine is constantly surging to the tapering off where I cannot drive it for bell of damage to the drive train. Any experienced solution?