my 1989 ford mustangf cuts off at every stop light

check for vacuum leaks

STAY AWAY FROM STOP LIGHTS, OR JUST DON'T STOP!!!! SORRY BUT I JUST COULDN'T HELP MYSELF!!!! I AGREE WITH SHAWN. ALWAYS LOOK FOR THE SIMPLEST, STUPIDEST THING FIRST.

idle circuit could be at fault

if it wont idle i would start by checking the TPS''throttle positioning sensor''the idle air sensor also might be bad also but usualy a bad idle air sensor will make engine rev all the time.

also check air filter, sometimes they never got changed and finally get to the point where the car wont run

get a code reader and see if any codes are being saved by the ecm..... is engine light on? could be any number of sensors, or a combination of a lot of little things

Check for vacuum leaks. it could be a dirty mass airflow sensor (MAF), or a dirty idle air control valve (IAC). You can remove both and clean them with some CRC spray cleaner.

Did you ever find out what it was?