check engine light flickers/motor dies

i just did a tune up on my 1990 325,new plugs(bosch double platnum),cap rotor,air filter.the car was running alright before but needed plugs filter ect.now i start the car and it runs really strong but then the check engine light comes on and the motor sputters,light goes out runs normal.at idle it idles smooth light comes on it sputters and sometimes dies.any ideas?

Did you by any chance bump the electrical connector on the idle air control, I would make sure that is tight.