question about the idle screw and why it does what it does

[EstoMax]

ok

so im tryin to get my idle with the TPS unplugged to go to 650 because when i unplugged it and started the car (fully warm) it decided to sit at a 1000, and i want to advance my timing a bit.

so i turned the idle screw in a bit and it dropped down to 800, but then as i kept turning til it wouldnt turn anymore it didnt drop anymore, as i turned it back out, beyond what it was, it made the intake hiss a lot, whats that caused by?

whats going on!?

TIAmax

[NISTECH]

Air is passing through a tight space into a vaccum. The point at which it is entering is where the hiss is coming from. It is the turbulance at that point creating the audible hiss. This is normal, however you should be able to turn your idle down till it dies or almost dies when the TPS is unplugged. What this means is you have air entering at another point allowing it to still run. You need to find the source of air ,be it a vaccum leak or a stuck open cold start air passage.

[EstoMax]

hmmm... what vaccuum leak could cause that? and from where?

stuck open cold start air passage.. wheres that?

thanks

[NISTECH]

The vaccum leak could be from anywhere like a vaccum hose not on, intake gasket, stuff like that.

The cold start is your air regulator, its black on one side and silver on the other has a small electrical connector near the idle control unit. It has a bimetal strip inside ,as it heats up it slowly closes off the additional air needed to start the car cold. If the valve does not close it will continue to supply extra air therefore increasing your idle speed. By closing off the idle screw will only lower it slightly as you have seen. If you can get to the hose coming off the back of that valve and its not brittle ,try pinching it to restrict its air flow while turning your idle screw in. If the car dies or alomst dies you found your problem. NOTE the car must be fully warmed up when you do this.