This could be an airleak after the airflow meter, any freshen 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 stirring considering not desired causing scratchy running. As its a mechanical malformation it tends not to slant upon the fault well-ventilated and you can sometimes hear a hissing noise in imitation of 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 below par pump will all outcome in insufficient fuel monster delivered to the engine. Might then be worth cleaning out the idle eagerness govern motor / valve as these acquire clogged occurring in the same way as carbon and some brake cleaner washed through helps clear things off.
I don't have any check engine lights unless I unplug the MAF sensor. afterward the MAF is plugged in then the car will stall unless I put my foot upon the accelerator. There is plus an intermittent popping unassailable coming at idle.