i have a 88 iroc-z 5.7 i can not figure out what is going on with it everyonce in a while she would hold an idle fine and then stop the next time i started it i have advance than reduce the timing to see if that would help and i have also changed the tps sensor and now she will not hold an idle at all if somebody has anything to help please let me know thanks bryan

 

Clean or replace the IAC (idle air control).