Well, to be quick about it. My idle is normally set to 900 rpm or so. Now, out of the blue, my idle will drop to like 6 or 7 hundred then go back to 900. This happens like once every few seconds and only at idle. No power loss or anything once I get moving. Although I have put on new exhaust and a tune, this was happening for like a week before I changed anything.

My coworker says that it is probably a vacuum hose and he said it would be a cheap fix. My check engine light is not on.

Thank you for any helpful replies.

 

My car also does this, especially once I pull it in the garage at night after I've been driving it. Haven't really inquired in to it though...

 

Has your car been tuned to idle at 900? I believe stock, mustangs idle at around 650.

 

Switch - Yeah that's standard or around that area, for me too.

I had idle problems for awhile and also would try to kill the car when idling.
I don't know what fixed my problem, but here is a few ideas.
Clean the MAF (Mass Air Flow Sensor)
Clean your Air Filter (not really nessary, but it's nice)
Clean the IAC (Idle Air Control)

 

Well, it still moves around no matter what its set to idle at. It happens whether or not I have been driving the car.

My air filter is clean, I would probably need to check those other two options though. thanks.

EDIT:

Hah I feel like a moron, my CAI's filer was halfway off. put it into place and tightened and its all good.

 

Haha it's all good. It happens to the best of us.

 

How does one actually clean the MAC/IAC? Yes, this is probably a n00b question, but to be honest I've never done this before and it's something I would like to do in the near future.

 

For the MAF you take it out and spray it down with "MAF cleaner" yes they sell a product called that. Or they sell electrical component cleaner. For the IAC or EGR I always use Carb cleaner or Throttle body cleaner and spray the **** out of it a few times.

 

Thanks Dustin. If I ever find something that you don't know I'm sending you ten dollars.

 

I've used Windex and a Q-tip with success as well.

 

I used the MAF Cleaner on the IAC. I hope that's not bad, my car is fine, besides that I just blew my clutch. FML

 

Its fine, but its not strong enough to actually clean the IAC or EGR out. As they get carbon build up and sludge from oil. SO Maf cleaner isn't gonna cut it on that stuff.