[RMC]

Your 87 is a OBD-I system. It does not store the code past when you turn off the key in most cases. It does keep coming on due to self test showing that an emission system part is out of specs. Best to find someone whom has the ability to read the OBD-I codes and have that person read the code before the car is shut off next time the light is on. Most auto parts stores only read OBD-II (96 and newer) codes. Some may have a reader that can check the older cars.

Doesn't this year still respond to shorting the A and B pins together on the computer diagnostic connector under the dash and getting a flashing SES light with the stored codes? Also, I do remember that some codes are stored for a period of time after the SES turns off.