Idle is controled by the IAC valve (idle air control) via the computer and
is not adjustable.
You can go over the system if your not happy with where it is idleing.
Proper idle for the V6 is roughly 900 RPM.
The set screw in the throttle body is for minimum air flow through the
throttle plate which is often misunderstood as the idle screw. Any tweaking
of the throttle stop screw will give the ECM fits. The ECM wants to be in
control of the idle and is not happy when it can't control it. If the normal
learn limits of the ECM are exceeded, they will be reset to nominal, causing
an erratic idle.
The IAC and associated passages need to be clean to work right. Remove the
IAC carefully. You can clean it (the nipple) using carb cleaner and a small
brass brush or rag. At this time also clean the throttle palte. Once clean,
install the IAC back in the throttle body and reconnect the IAC wires.
For the ECM to properly control idle, the throttle stop screw must be set
for "minimum air". This is a process that sets the idle with the IAC fully
extended. To fully extend the IAC, jumper ALDL pins A and B together (just
like when you check codes) and turn the key on, but do not start the car.
With the key on, not running, and in diags mode, the ECM will keep trying to
fully extend the IAC. After 30 seconds or so, pull the IAC connector off the
IAC *before* doing anything else. This will capture the IAC fully extended.
Now pull out the jumper in the ALDL, and start the car. Typically the
"minimum air" idle speed is in the 500 RPM range. I find the car can bearly
run at 550. So as long as you can get it to idle on its own between 600 &
700 your good. Set the idle using the throttle stop screw. (The engine
should be fully warm to do this.) Now shut the engine off and reconnect the
IAC wires. The ECM does not know where the IAC present position is, so pull
the ECM fuse (or disconnect the battery) for 20-30 seconds. (This will cause
a complete ECM reset of all learned parameters, including the learned IAC
ones. Then reinstall the ECM fuse.
Turn the key on, wait 10 seconds or so, and turn the key back off. This will
now reset the IAC to a known key-off "park" position. Now start the car. The
engine should idle properly under control of the ECM. There are some learned
values, such as an IAC offset for A/C, etc that need to be learned, but this
will happen under normal driving conditions. I suggest driving the car right
away under all conditions. Stop & go, steady cruising over 45 mph, full
throttle, and so on. Pull over a few times and turn the car off, then
restart it. The IAC can only learn X amount of counts with each run
position. If everything else on the engine is in good condition and
operating properly it should be around 900 RPM after coming to a complete
stop with slight variations and improve over time.
