This could be an airleak after the airflow meter, any freshen dragged in here isn t seen by the ECU and as a result not compensated for and can thin the engine out and can next allow the engine to rev up taking into consideration not desired causing harsh running. As its a mechanical anomaly it tends not to incline on the fault fresh and you can sometimes listen a hissing noise later the engine running.
I started the car occurring this morning, it starts up and runs at 1750 and within a minute or suitably climbs greater than 2500.. It is supervision mild though, just pretension cutting edge than it should be. I moreover checked the throttle screw plate/return screw, on purpose turned it out and nothing changed. put it support to exactly where it was. No vacuum leak sounds and every connections verified. I character good very nearly them as I've been in there a bunch of times..
This could be a large vacuum leak ,with the MAF joined it is deserted measuring the let breathe that is getting gone the MAF, therefore if the intake manifold is sucking in air the expose to fuel ratio will be unconditionally out and cause the engine to stall. If MAF is disconnected the engine goes into a limp measurement and lets the engine run. behind carb cleaner spray spray in the area of the hissing once the engine processing and in the manner of you listen the engine stall or rev superior there is the leak ,could be a bad vacuum hose bad gasket on the manifold.