How do you reset the idle air control valve?
bwysocki
Have 95 LTI. Recently installed higher-stall
torque converter which is lighter than the
stock one. Noticed after warm-up the
ECM was hunting proper idle.
??Can someone post procedure to reset??
Thanks
Steve LeBlanc
bwysocki wrote in message <6jlevc$l1v$1...@news0-alterdial.uu.net>...
Pulled shamelessly from www.f-body.org
IDLE AIR CONTROL (IAC) VALVE RESETTING
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. Doing this assumes a working knowledge
of your engine, and basic hand tools and an accurate tach are needed (a scan
tool is ideal).
The IAC and associated passages need to be clean to work right. Remove the
IAC. If the car has significant mileage, it may be dirty. You can clean it
using carb cleaner and a small brass brush. At this time also clean the IAC
passages in the throttle body. 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, 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 10
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 400 to 500 RPM range, so you may need the manual for the spec for your
model year and engine. Set the idle to spec (if you have no spec, try 450
RPM) 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 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. But if
the idle is now still out of control, you have other problems.
