I have a 1990 delta 88 and the engine light is on

the part is a paperclip. Inserted in A & B sockets of the diagnostic connector. You must then count the flashes. long flashes 1st, followed by short flashes. the longs indicate 10, the shorts are 1. so 2 longs and 3 shorts would be a code 23, 4 longs and 2 shorts would be a 42...etc etc. after the shorts finish, there will be a semi-long pause, then it will start flashing longs and shorts again. watch and count flasghes AGAIN carefully. if its the same as before, that is your only code. It MAY be a different number, meaning you have more than 1 code. count them long/short sequences 1 after another and write them down till you have them all saved. Then search them on the internet or repost them and if I happen to see it, I may be able to lead you further.

This work is usually done with expensive tools for a reason. flash codes are a basic and limited diag step...replacing parts based on what they tell you can waste hundreds of dollars if its not an obvious problem, so be careful before buying parts just because you get a code for o2 sensor rich or MAP sensor voltage high. Its not always the part mentioned in the code, that may in fact simply be the sensor alerting you it sees a mechanical problem and the sensor is in fact accurate. The car may BE rich, or there may BE a big vacuum leak...etc etc. If you arent comfortable with the troubleshooting, dont be afraid to take it to a professional.