CCF5000

Just curious whenever i start my car it fires and then it drops to 500 rpms goes up to 1200 and then repeats this process for a while until it finds the idle point. Also if i rev the car a little bit with the throttle body it revs then the rpms jump down and go up like surging. I tryed to look for vaccum leaks but i really cant find one there is a quiet hissing at the back of the upper intake but i doubt that that is leaking i torqued all those bolts to spec and used a new gasket last time i had it off. We did have the injectors out of the rails though and reused the orings because we were careful with them. Are u supposed to use new o rings?

91stang

it sounds like a vacuum leak tho.. recheck yourself in the back of the upper intake (there are a bunch of widden wires back there) also if you want you can clean out your throttle body cause it could be sticking and take off your idle air control vavle and spray it down real good with carb cleaner

midnight50blues

I had the same problem with mine. I found the answer on search. I clean the **** out of my throttle body, intakeand idle air control vavle with the brake cleaner and seafoam. It runs great and alot smoother. Give it a try.

Scalihoo

I had asome idle surging happen to me today for the first time on a low milage restored car, I pulled over & put pressure with my thumb on that little springedflange where the throttle cable hooks up & she dropped back down to normal, but came back a little driving home. I then siliconed sprayed that little spring, took it for a nice ride & it seemsfine..
Seems theres 10 pin " salt & pepper " connecters behind the intake plenum that in most cases have to be cleaned & maybe replaced when this condition happens with many fox mustangs, but I believe mine just needed a shot of silicone.. but time will tell