Until a couple weeks ago, i could go out & start my Bronco up, and it would idle fast, until it got warmed up some, and then it would kick down to it's normal idle... Now, it won't fast idle, and will die. If I rev it up, it runs rough... Then if I let off, it will drop down and either die, or almost die & cycle up & down... I tried to pull codes, but can't make heads or tails from the beeps... Anyone know a common cause of this?

 

That is caused by a faulty iac(idle air control) valve. Also, clean the throttle plate. The iac you can find at any parts store. To make sure you get the right one, get the Ford engineering number off the part. It will probably be something like E7TF-9F715-A1A or some other variation.

 

I agree. It should be the IAC Valve. My 85 EFI, 87 EFI, and 95 EFI have all had the same symptoms corrected by replacing the valve.

 

Thanks guys, I thought that it was probably the IAC too... I'll go get one today!

 

Well, I got the IAC solinoid off...(the little part with the connector held on by 2 small screws) Is this what goes bad? or do I need to replace the whole IAC valve assembly? (the part this small part screws to)
Thanks again.

 

Dave, your Bronco is the same year and engine as mine. The IAC is mounted on the side of the throttle body where the 2 intake tubes come in. Take the entire unit off of the throttle body. I would suggest you buy the entire unit as the pintle in the vavle body is probably coked pretty bad. Replacing the IAC motor only most likely will result in an unsatisfactory fix and I'm not sure you can find the motor only part.

 

You'll be buying the whole valve & motor assembly, but you can't drive with it off - the engine won't idle down because of the MASSIVE vacuum leak. BTW How does it run with the motor off? The same? Be sure to clear the codes when you get the new one on - it'll probably be best to disconnect the battery for a few minutes to clear the computer's adaptive strategy since it's been learing how to work with that faulty IAC.