Stalling at idle, Help please!

[kpw]

My wife called, stuck in parking lot, with our '99 4.0L Sport. The engine would start, but not idle. Everytime she went for reverse, it stalled. When I came to the rescue I could see nothing amiss under the hood with a quick look.

I was able to drive it home by starting in neutral and keeping revs above 1,500 and dropping into drive. Seems to run fine it just won't idle without stalling. I'll dig into this tomorrow morning, but basically stopped working on cars back before they were injected and computerized. This vehicle has 60K and has been running well. Plugs and wires were replaced at 32K which cured poor performance and missing.

I'm hoping those who are knowledgable on this board might be familiar with this problem and steer me in the right direction. Thanks in advance for any help/response.

 

[Alec]

Welcome to the site!

Might be the IAC (idle air control) valve preventing a proper idle. This is actually a fairly common problem, and there are many threads on it. From what you said, that's my opinion. A new one is about $70 from Ford and replacing it takes a few sockets and about 10 minutes.

 

[kpw]

IAC Questions

Alec, Thanks for the info and for your welcome . Did a search on IAC valve and several have suggested cleaning it. I'm sure I can replace it if it's toast, but might not spend the $70 on speculation. Several questions: 1) Is there a test to tell if IAC valve is defective? 2) Where is it located? 3) How can I clean it (if it can be cleaned)?

Thanks again for your help!

 

[Alec]

1) you can test the voltages from the wires but I dunno how.
2) it's a cylinder bolted to the intake just behind the throttle body with 2 bolts; with a 3 (or 2?) wire harness to it.
3) there are cleaning procedures outlined in some other threads.

 

[kpw]

Alec,

Did more research on IAC threads, and agree with your diagnosis at this point. Tomorrow I'll pull it , explore it, clean it and if I think that's the problem I'll replace it.

I'll let you know what happens. Thanks again...

 

[Alec]

no problem, good luck.

Glad you found us!

 

[kpw]

IAC Cleaning Success!!

What an easy fix and for zero dollars. All of life's porblems should be so easily resolved. Here's what worked for me:

Pull the plastic shroud that covers the intake manifold and there the IAC (Intake Air Control) valve is, right on top. Pull the two wire connector, and remove the two small bolts and there it is in your hand. The IAC has what appears to be a solinoid attached to a plunger that controls a valve between two chambers. The IAC basically admits the correct amount of air for proper idle under varying conditions. Mine was stuck with carbon, hence the stalling.

For cleaning I filled the chambers with Gumout, soaked for 10 minutes, then blew it out with compressed air. I did this three times and most importantly, I had to reach in with needle nose pliers and carefully pull the valve unstuck (didn't take much pressure but wasn't coming free on it's own).

While I was at I replaced the air filter, which was due. I also disconnected the battery ground to reset the computer, not sure if this was necessary but I knew it wouldn't hurt. Then a quick re-assembly and voila, it started right up and immediately settled into a smooth idle. A test drive and happiness reigns supreme.

I have a strong feeling that nothing is functionally wrong with my IAC valve and that it was just dirty and sticky. Time will tell. If it fails again then I'll replace it. Oh, after the test drive I changed the oil & filter which I do every 5K. I'm feeling like a virtuous guy...

Thanks to Alec for the quick and accurate diganosis. And thanks to all the members & powers that be for this great forum. And I love my Explorer!

 

[X24]

Glad that worked for you. I had the same problem with mine but I just replaced it. I read that cleaning it works but not for that long. You seem very helpful... hope you stick around.

 

[Opera House]

Did you pull off the black plastic cap

and clean the filter on the IAC? There is a little felt density filter that gets glogged. This allows fresh clean air in past the shaft so that deposits don't build up. Pry under it and the top portion pops right off. Most times just pulling out the element and flicking it with your finger a few times is enough. Do you live on a dirt road up there by LG?.

 

[kpw]

No Opera House, I didn't clean or even see the filter. And, given the tight confines and limited access didn't feel comfortable doing more digging than I did. The valve has a steel shaft through the middle, the filter must have a hole as well?

I do feel that given the thorough, multliple Gumout soakings and 100psi air blasts that the filter may be clean now anyway, I hope so.

Not many dirt roads here, but I do get back in the woods occasionally...

One thing I did notice is the slack in my throttle cable. Thought about adjusting the butterfly valve screw to make it up but wasn't sure. I have a very slight but noticeable delay with the gas pedal. Know anything about that? Thanks.

 

[X24]

Yeah, most people just use some zipties around the cable down by the pedal to take up the slack. Thats what I did.

 

[kpw]

Good idea, I'll take a look. Thanks

 

[steve_burton]

G'day,
had the same thing last week, Ford replaced the O2 sensor running fine now.

Cheers Steve