Why is your 1987 Chevy Celebrity stall when is come to a stop?
This sounds like an idle problem. Does the service engine light
come on before the engine stalls? If it does it should post a code.
Knowing what that code is could lead to a more accurate assessment
of the problem. Does the engine idle ok before you put the car in
gear? Does the engine restart and idle ok after the stall?
There are multiple possible causes for the stall. The IAC, idle
air controller, could simply be dirty and not delivering enough air
for the engine to run. If the MAF, mass air flow sensor, if faulty
or dirty that might cause the engine to stall. If the Oxygen sensor
is faulty that could cause a stall and generally poor running as
well. It may be possible that if the TPS, throttle position sensor,
is faulty that could cause the engine to stall at idle speed.
If you have found out what the problem is I would be interested
to know for future reference.