Reply to thread

Message: <blockquote data-quote="NERD" data-source="post: 630364" data-attributes="member: 8956">"Cliff"The screw you have been adjusting is not an idle adjustment screw, it is a throttle stop screw used to set the intial airbleed through the TB, so that the PCM can then control the idle by varying air flow through the Idle Air Control (that's why it's called that).Here 's the procedure for getting the TB stop screw adjustment back to where it's supposed to be.<a href="http://www.paladinmicro.com/PalMFrame00.htm?wks=tba" target="_blank">http://www.paladinmicro.com/PalMFrame00.htm?wks=tba</a>The only way to change the idle speed is in the tune, the stop screw being only used to preset the amount of air bleed through the TB when the throttle is closed. It is set so that with the throttle closed the IAC is operating in the lower 15% to 20% of it's range when the PCM is controlling the idle speed to provide some "headroom" when low idle speeds are desired and quite a bit of room to increase idle.Using it (the stop screw) to attempt to control idle speed is a futile task because the PCM will just increase or reduce flow through the IAC to get back to the programmed idle speeds (there are several programed speeds depending on IAT, ECT, load, etc).If the stop screw is tightened too much, in an attempt to increase idle speed, then at some point too much air will be bleeding through the TB and the PCM will not be able to control the idle even with the IAC completely closed--this generally results in the idle speed being erratic as heck as the PCM tries its best to maintain control.If it loosened too much to attempt to reduce the idle, the PCM will increase flow through the IAC to keep the programmed speed. It can do this with reasonable success however the engine is likely to stall when the PCM suddenly stops IAC flow (for deceleration, etc.) and there if far too little air bleed through the TB to keep the engine running. At the extreme the throttle plate will stick closed due to engine vacuum, binding, and stiction...Disconnecting the battery will clear the KAM (Keep Alive Memory) and force the PCM to relearn the idle air trims needed to maintain the programmed idle speeds, however eventually it will relearn the trims anyway.</blockquote>