A lot of people (including myself) have been complaining of poor idle issues and IAC problems. And a lot of people say they buy new ones and still havent fixed the problem. I, for one, have replaced my IAC twice, due to some problem with how they make them in the parts manufacturing plants in mexico. I replaced mine the first time, and noticed right from the start that there was no spring around the shaft inside that controlled the plug that fluxuates to control airflow... the original one had it... but when i installed the new one, it ran fine... still had the "shivering" at idle... so today i went down to another auto zone (different city) and did a warranty return... the new part had the spring inside, and i also noticed that the nose of the air channel on the outside had been machined down a bit, and was also a small bit wider than the part i got originally... i put the new one on, and while the shiver is still there... it cut down tremendously, almost to the point where you dont even notice it anymore... so i guess the moral of this story is to make sure that thing has the damn spring!!!! lol dont know why the other one didnt have it, or why it worked without one...but i know the spring made the difference in my case. Hope this helps out someone else in the same boat

 

Another reason not to buy parts at Auto Zone!

 

i paid $50 bucks for that part at auto zone..... how much you think that woulda cost at motorcraft? lol all about price... works now though... the trick is just to make sure its the proper design.

 

Over the counter price at a dealer is usually double, but before you get the part, they make you give them your pcm calibration to make sure it is the part specifically for your application. How many questions did Auto Zone ask? I think none except for model and engine size and year. No calibration

Robbie

 

I know it doesn't always work but when my truck wouldn't idle I just cleaned the IAC. Take it off and spray it with brake cleaner real good. Mines been working fine for about 10,000 miles.

 

At my shop I always buy the IAC's at the dealer.

They work, fit and zero complaints.

 

Iv'e heard many, many complaints about the IAC'S bought at Auto Zone

 

well i know mine is working fine now... wasnt before, but ill see about getting one from the dealer later on this one seems to be worknig fine, so... it aint broke, and i aint fixin it lol

 

okay now this makes me wonder. I just replaced my IAC from reading posts because my idle is off the charts as soon as I start the truck it increase to 2000 rpm. When I took old IAC off I noticed the spring and I noticed the new IAC didn't have a spring. I just assumed that since the original IAC was made several years ago maybe the part design had been changed a little. Anyway to my point, the new IAC did not make any difference. My truck still idles up to 2000 rpm, wonder if the new IAC is bad? Or if it is something entirely different.

 

no, mine worked without the spring... the idle was just a little rougher... i mean it COULD be the issue, but i would look into something else... my estimations tell me you probably have a vaccum leak... ever try to take your PCV valve line off the valve while the motor is running? you will notice a jump in idle speed.... maybe its just the gasket for the throttle body.... or maybe its something bigger..... the only way to tell is hook up a vaccum guage to your system and see what you are pulling in reference to what its supposed to be pulling... if that checks out okay, then your vaccum is fine... other than that? maybe a faulty TPS sensor?

 

I replaced TPS today and it fixed it. Thanks for your help.

 

WHAT isn't known about the operation of the IAC is that it is
"pulsed" by the PCM and needs the spring for the piston to work against so the very fine control that it is capable of will be obtained.
The piston position controls the air bypass. This spring is needed to keep pressure against the magnetic operation of the piston valve solenoid so it will always tend to stay in it's min position as governed by the pulses from the PCM.
Since exhaust and crank case oils form in this area, the IAC movement becomes sluggish and won't follow the signals from the PCM in a faithful manner.

 

then how come mine worked? not flaming, just asking.

 

Most of the Ford IAC valves no longer have the spring in them either. Personally, I use only Ford or Motorcraft electrical or electronic parts, because generally the aftermarket ones are junk.