ive been having a problem that is getting worse latley, every time i come to a stop my car stumbles at like 400 rpm then eventually works its way back up to 950 rpm, and once it stalled while turning and slowing down.

things that have been changed:

plugs
wires
opti (3k miles old)
ac delco 02 sensors


i have a 58mm bbk throttle body that i put on last year but ive havent had any problems till about 2 months ago, could a bad iac be the case? how do i test it and find out if its bad

i also had my tune changed because of a new converter and i put in a aftermarket maf last year when i did the throttlebody

 

ok it only happens when the engine is warmed up or in closed loop because i shut it off then restarted it and stoped and it was fine but when it went back into closed loop and i came to another stop sign it stumbled again.

i also cleaned my tb and changed my iac and reset the position according to shoboxe's page

 

theres a thread somewhere on here about cleaning the MAF.
I don't know if thats your problem, but it sounds like a good idea.

 

Your going to need to data log the car to see the IAC values and what it is doing, to accurately see what is going on with it.

 

i need software to datalog ill do that this week.

i disconected the iac and went for a drive and it was fine when comming to a stop even pulled over and pluged it back in and it still drove fine but when i restarted it when it was pluged in, it started to stumble again, what causes the iac to act up? i replaced it with another used one