I have V6, 3800 that will not idle under 1800 to 2000 rpms. changed idle control valve,checked for any vacum leaks, including intake manfold, nothing. Removed and reconnected power.
high idle speed on 1993 Buick LeSabre
I have found that the throttle body to intake manifold gasket splits on these engines and that will cause a very high idle. It acts like the throttle blade is open too far. Also, what is the TPS reading. It should not read above .5-.6 volts max. If it does, the Computer will think that the car needs power and will open the IAC with the presumed opening of the throttle. Hope this is a help. Do you have a Check Engine Light on? If so, you can pull a code and see what it says this could be big help. Also if your Charging System is weak, the computer will boost the idle to help charge the Battery. Is there a Battery Light On?
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Seems to me that the idle speed control motor needs to be reset to the desired speed by using a special tool that tells the pcm that it is at idle or off idle which then takes care of the amount of fuel and air mix.This needs to be done this way to set the pintle in the valve because the idle setting is nonadjustable.This thing plugs into the IAC motor and the the other end into the harness that feeds it