When coming off accel/boost and you allow the car to coast and the revs drop back to idle, how much drop is ok?

Obviously if it drops to the point of stall that is bad and means there is something wrong; vac leak? or ISV ?

But what if there is a lot of drop to almost a stall or slug on the motor but does not stall. Is that ok? Does that mean there is a vac leak/bad ISV but not real bad?

Is it a simple adjustment of the idle screw needed? or is that masking the issue?

In my case when the ac is running it seems more of an issue as the idle is slightly lower with ac engaged than not.

 

Have you gone through the idle setting procedure of disabling the idle stabilizer then setting your idle speed? If the air adjustment has gone off or you have some other leak, then this may fix it. If it still falls through and you can change only the idle mixture try leaning it out a bit.

 

i used the idle adjust screw, not idle stop, to bring the turns up a little.

87951