89 Chevy Celebrity diagnostic code

I've grounded the terminal and the service engine soon light flashes 1-2 in sequence, telling me the memory is working. After ungrounding the terminal. I started the car and idled up to temperature. The service engine soon light, then re-lights. I then re-ground, while idling, for the trouble code, but it flashes, repeatedly, on and off. No number to gather from what it's doing. I counted repetitive flashes into the low 100's before ungrounding. I turned off ignition, reset key in the on position, but without starting it, reground the terminal and then the check engne light is back to repeating the 1-2 code sequence. Any pointers would be helpful at this point. Engine becomes rough on decceleration and stalls frequently, but always re-starts. Just removed and cleaned all plugs, which were fouled. Slight improvement, but still a rough ride. Thanks in advance!!!!!


HAPPY BIRTHDAY TO ME!!!!!!!!!!!
T359

Obtained codes, replaced MAP sensor, O2 sensor and cleaned EGR valve. Vehicles runs smooth again and I have re-set computer and no error codes present. Woooooooooohoooooo!