I have a 1989 Sierra 1500 with a 305 & 400 hydramatic tranny. For the past month it has been running rough on startup until it warms up. The engine shakes and the idler pulley jumps up and down.
The IAC was replaced this week and now it comes up on a 2000 rpm idle on start (didn't before) but it still runs rough. MAP sensor was replaced 2 months ago.
Any ideas on why it runs rough just when cold?

 

no ses lite?...maybe a vacuum leak at the tbi gasket..they were bad about leaking there

 

No SES lite. TBI Gasket, no sure but I heard it would idle high if that was an issue. I just put it through and emissions test and it passed.