Yeah so ive had this problem for a few months now and i cant seem to track it down. I have changed my iac valve and that didnt do it. vaccum is at 19"hg
I realized that my fuel pressure was at 60 psi at idle in park so i thought maybe its overpowering the stock injectors and its loading up on fuel. it only does it at idle in gear. when its in park or neutral it resembles a light miss but it doesnt stumble bad,almost die then surges like it does in drive sitting at a light. i replaced the fuel pressure regulator with a new factory spec on and the fuel psi is still reading 60 at idle and in gear and at wot in park its going up to 70psi Any ideas why its so high? the fuel pump is stock.

 

My first guess is a previous owner installed an adjustable regulator and set the pressure too high. If the stock regulator failed it would most likely be reading low, not high. It's a possibility though that the stock regulator failed. I would also check for restrictions in the fuel return line as that would cause the fuel pressure to be unusually high.

 

ahhh the fuel return line, having some blockage in it somewhere would make sense to me why the pressure could be so high. I wonder if there is a check valve somewhere in the return line between the rail and the tank? hmm thanks for the idea!