Cold start--up and down idle

[Deths91Gt]

I know this is a newbie question--i just recently got back into the Mustang scene. But everyone of my cars ive had over the last 10 years have idled like crap when cold--i have to sit there and rev the motor up until it will stay at the same RPM. Is it the IAC?? Doesnt seem to be a vacuum leak--car runs and idles fine when its warmed up. Major Mods consist of E-cam and Longtubes and H-pipe--its a Speed Density but even my MAS cars have done this. Thanks.

 

[PsYLenT-G]

I have an all stock 91 GT and have a similar problem. see my thread for more information: 'Idle issues... Can anyone help? '

 

[staticc]

im right in the same boat. longtube and b cam.

 

[xplo89gt]

same boat, didnt start happening til i installed heads, intake, tfs stage 1 cam.

i've checked about everything except the ECT sensor. I will probably replace that ($30) to see.

 

[HO5POINTO1990]

I have the same problem but not when cold but rather THE SECOND START... i start it the first time and there are no problems... but then when i start it again that day or anytime that day it doesn't idle correctly. It kinda bounces up and down till it fixes itself... or i rev it up once or twice to get it to stay above 750 rpms. Oh well.

 

[DirtyD916]

get some carb cleaner and clean out the throttle body. Then clean out all the hoses and connections involved or connected to the throttle body. Also adjust the idle on the throttle body.
Just remember that most cars dont strat good in the cold. just let it warm up.