On startup idles really choppy at or below 500 rpm, putting it in drive it lurches and jumps forward sporadically. If I rev it in park or continue to give it gas in drive something just catches and it goes back to normal idle and its fine until I have to start the car again. To me it sounds like a cylinder mis-fireing or not firing at all. What do you guys think?

89 Iroc-Z 350.

 

clean the idle motor and passages

 

check your IAC

 

pulled out the IAC and the spring and metal pin inside were black with carbon. Put it back in started up and it was low and choppy and then the next 4 starts it turned over and immediately died, which its never done before. Now its back to low and choppy consistently. Possible bad IAC?