Two
things I would suspect first of all. The first is the idle air control
valve (IAC). It is a computer controlled solenoid valve that opens to
admit varying amounts of air into the engine at idle. The IAC has
a passage that allows the air coming into the engine to bypass the
closed throttle. The computer adjusts the amount of air to control idle
speed by opening the valve fully for maximum airflow or closing
the valve for minimal flow. Sometimes the IAC will begin to become
sticky and it will not move when commanded by the computer. So the
engine may starve for air and stall. If this is the case, the IAC can
be cleaned with throttle body spray cleaner available at the auto parts
store. The IAC passageway can usually be seen once the air intake
tubing is removed from the throttle body. Spray some cleaner into the
passage, start the engine and let it idle. Keep spraying bursts of
cleaner into the passageway, pausing to let the engine recover speed as
it will start to stall when the spray enters. The IAC can be removed
for more thorough cleaning, or it can be replaced.
This page has more info on the IAC:
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/0e/55/ff/0900823d800e55ff.jsp
The other possibility is that the Torque Converter Clutch solenoid is
failing. It controls the flow of transmission fluid to the clutch that
locks the torque converter. The intent of the clutch is to improve fuel
economy by preventing torque converter slippage at cruise. The clutch
is only applied when the car is moving at fairly constant speed. Then
when the vehicle is slowing down the engine control computer unlocks the
clutch by controlling the TCC solenoid. If the solenoid fails and the
clutch stays applied as the vehicle is coming to a stop, the engine
will shudder and die just like on a manual transmission car that comes
to a stop without pressing the clutch pedal. A failed solenoid can
simply be unplugged to disable the clutch feature. Fuel economy may go
down slightly, but the car can be driven safely with no worries until
the solenoid can be replaced. A transmission shop could help you find the connector for the TCC solenoid.
TCC connector is in this picture:
Images available only to Customers.
It
is the connector on the left side with the horizontal line showing
where it connects. This is on the front-facing side of the
transmission, on the driver side under the hood. It may be a light blue
colored connector. The TCC connector could be disconnected for testing.
Reconnect it if the shudder/stall persists when TCC is disconnected.
Edited by babarche on November 5 2005 at 8:34 PM