God damn surging idle!

[68mustang5.0]

Alright, this has been happening since i got the car.

Everytime i start up the car, if its still cold, the idle will surge, even when coming to a stop. The RPM's will drop, then rise back up, drop, then rise back up. One time it got so bad, that when i was at a stoplight, the car dropped idle so bad that the motor stalled...the light turned green as soon as that happened, had to pop it back into neutral and then start it back up....with a line of cars behind me. :nonono: :slap:

First i took off the IAC, and cleaned the holy hell out of it....no avail. Then, i thought the TP sensor was the culprit...replaced it, checked the voltage, all good....still surging. Then, i cleaned the MAF element, still no avail. Then, i rechecked my CAI piping to make sure it was tight....still no avail!

right now, i have no clue what to do. it seems like ive tried everything, but it didnt work. It happened this morning, as i was leaving my house...coming to a light, slowing down....did the surging again. it also happens when the car is warm...In park, i would rev the motor, and the RPMS would drop.....sometimes the car would die, sometimes it seems like it wants to, but just gains RPMs again...drop down, gain RPMS.....damn neverending cycle.

Any ideas?


Thanks guys!

 

[ripper]

IMO surging is always your IAC. No matter how much you clean them you never get it clean enough. That carbon is like concrete sometimes. Unplug it and turn your idle screw on your t/b/ till it idles about 9k. Drive it and see if it still surges. If no surge you need to replace it.

 

[scarface]

IMO surging is always your IAC. No matter how much you clean them you never get it clean enough. That carbon is like concrete sometimes. Unplug it and turn your idle screw on your t/b/ till it idles about 9k. Drive it and see if it still surges. If no surge you need to replace it.

I couldnt have said it better Steve, IAC is a funny little beast.

 

[68mustang5.0]

IMO surging is always your IAC. No matter how much you clean them you never get it clean enough. That carbon is like concrete sometimes. Unplug it and turn your idle screw on your t/b/ till it idles about 9k. Drive it and see if it still surges. If no surge you need to replace it.

Wheres this idle screw? i thought only the 5.0s had that? i have a 4.6

 

[ripper]

I have an Accufab t/b but im sure theres one on the stock t/b Uh i think :dunno: lemme see if i can find a pic Its were the black arrow lookin thing is pointing lol

[attachment deleted by admin]

 

[68mustang5.0]

I found the screw, but i cant fricking adjust it! stock TB.

so now do i just go out and get another IAC? or an aftermarket TB? :lol: ^-^

 

[ripper]

When you unplug it does the car still run? Unplug it see if you can keep it running. If theres no surge than go get a new one. There like 40 bux. You dont need a new T/B lol.

 

[68mustang5.0]

I went out, started the car, unplugged the IAC, it just died right off. So do i need a new IAC?

 

[ripper]

No but ill bet thats what it is. When mine was surging i turned the idle up with the screw and unplugged it till i got a new one. Its a temporary fix. After i got the new one it still had a slight surge but we fixed it in my tune. If you have never changed it my guess is thats your problem. I know 40 bux isnt nothin but if its old you need to change it. Try it.