On Satruday, I put my 03 SportTrac in reverse and the truck began to roll backward in very noticeable surges. I was looking over my shoulder at the time and not watching my RPMs, but I could hear the engine rev. I was working the brake while reversing, never hitting the gas. I pulled out of the parking lot and drove about 1/4 of mile until I came to a stop at a red light. Once stopped and idiling, the engine began surging to 2K RPM and then down to 0...it never stalled but acted like it wanted to, then surged back to 2K RPM. I also noticed that when the RPM dropped to around 0, the oil gauge would go down, and then come back up to a normal level when the engine surged. I didn't pay attention to the other gauges. I turned it off, re-started, and it has acted OK ever since. Does this sound like an IAC problem or something else?

Before this episode, I thought that I may have a failing IAC because at Idle, I get a little shake in the engine about ever 6-7 seconds, but it's barely noticable. I have never experienced a surge like I felt on Saturday.

Thanks

 

That sounds like a possibility.
It does no harm to remove the IAC and clean it carefully with carb or throttle body cleaner.
If you catch it early enough it might save you buying one!

 

Thanks allan. Any special procedures for cleaning? I have read on other posts where people recommend soaking the IAC in cleaner, while others say to use a cotton swab. Would like to know if you have suggestions. Further, I have started to shop around for the best deal on the part in case I have to buy one...is it sometimes referred to "Idle Air Control Motor" as opposed to "Idle Air Control Valve?"

Thanks again.

 

I soaked mine in TB cleaner overnight.
I pulled off the black "****"(which looks like might be a crude air filter that stops crud getting sucked into the works as the valve opens & closes) and plugged the spigot it sits on with duct tape.
Then I just found someplace to set it down so I could fill it right up and let it soak for as long as I could.
IIRC there are a couple of simple electrical tests you can do with an ohm-meter to make sure it isn't shorted out but to be honest the symptoms you describe seem to indicate that the valve is working but sticking sometimes.... I'd try the TB cleaner first and maybe look up a reference in the forums here to testing the valve electrically while you're letting it soak.
As long as you're careful I can't see any harm in using a cotton swab or even an old toothbrush; agitating any kind of solvent will often help it work faster on heavy soiling no matter what you're trying to clean, but I didn't do that.

As to Idle Air Control "motor": Ford, Motorcraft and most all of the parts places refer to them as IAC "valves".
Some other makers such as GM might use a slightly different device powered by a motor rather than a solenoid valve which Ford uses.
I do know that (forgive me, I'm in the UK so our terms are different to some of yours), for the power door locks, over here Ford uses another solenoid device but GM uses motors...totally off-topic but it just shows how some makers have different ways and mechanisms for doing the same thing. To buy one of those you buy a "central door locking solenoid" from Ford and a "central door locking motor" from GM.

If you're shopping around, try some of the online vendors listed left of this page. I've heard good things about rockauto.com but when I tried to get them to quote me shipping to the UK (which they say they do on their website) I couldn't get a straight answer from them. It wouldn't put me off from trying to use them if I lived in the USA, their domestic service seems good from others' comments here.

But whatever you do, make absolutely sure you take the OEM part# down and make sure you order the correct part. It's stamped around the edge of the valve's mating seat, around where the mounting bolts go. I had a heck of a job with mine as the part # listed was different (but very close and confusing). In the end I found my truck was a very late build for the model year, only a few weeks from the year-end and had a "next year's" IAC valve fitted!
If I lived in the USA it wouldn't have ben a problem but shipping, paying import duty & taxes, then having to have it all refunded and paying again when the correct part came was a PITA for a little half-pound valve!

 

Allan,

I can't thank you enough for the reply...I will definately be trying the procedure over the weekend. A couple of questions before I start though. First, the black "****" you described, is that on the inside of the IAC? I was looking at the valve last night and I don't remember seeing any type of ****. The only black piece on the valve was the electrical connection port.

Second, if I understand you correctly, I should take the valve off, put a piece of duct tape over the two holes that the valve covers, and then fill up both chambers in the IAC with TB cleaner. Is this correct.

Lastly, and again, thanks for your patience, after soaking, should I rinse the IAC with water or something, and then let it air dry? And should I do anything to try and clean the area you said to cover with duct tape? Thanks

 

If yours doesn't have the "****" type vent, don't worry. I've seen several different shapes of IAC on various models and I wouldn't be surprised if I saw an IAC that didn't have one at all.
It's a round, black plastic **** about the size of a thumbnail on the outside of the valve. If you first looked at it you could be forgiven for thinking it was some kind of adjustment control, like a volume **** on your stereo.
If you don't have the **** you don't have to worry about what I said about the duct tape, just make sure that you can fill it right up so that all the working parts are covered in solvent and prop or wedge it someplace for as long as possible for the stuff to work.
You don't need to do anything to it once you're finished cleaning, the throttle body cleaner will evaporate away quickly. If it was really, really dirty and there's still some residue left after you pour away the TB cleaner you might want to hold it out in the open air and blast it with the TB cleaner aerosol to finish the job.
You'll see what I mean when you get into it; just get it filled with cleaner & let it do its job.
Good luck!

 

Thanks again Allan. I will attempt the procedure over the weekend and post my results thereafter.

 

Well, I cleaned my IAC Saturday night. I filled the chambers with TB cleaner and let it soak overnight. I also went ahead and performed the electrical tests on the IAC and its power supply...everything checked out.

On Sunday, I noticed that the shimmy I felt at idle seemed to disappear, but came back today. But I haven't experienced the idle surge I described in my originial post since March 11. Any other suggestions for trying to eliminate the idle shimmy?

Lastly...what kind of TB cleaner should I have used to clean the IAC? The only cleaner I could find at AutoZone was an aerosol can that I lightly sprayed over the chambers until they were filled with fluid. Was this the best choice?

 

That's pretty much what I did.
The shake in the engine won't be the IAC, I don't think.
It sounds like a misfire or stutter; it may be a dirty plug or plug wire starting to break down or you might have get it diagnosed or let it develop into something definite.
It sounds like you've got the surging RPM's sorted, which was the IAC sticking. That's the biggie as fas as safety is concerned, as to the rest I'd check the plugs & wires.
I'm gonna be offline for the next month so I won't be able to add any more, sorry.
Good luck.

 

Thanks Allan, I appreciate all the help.

 

You might try cleaning the engine top out with SeaFoam. If the problem is carbon buildup it will clean the system.