Could it be coming from the A/C? You said it only did it when the engine was hot with the A/C on. Does it stop when you turn off A/C? If it does then try uping the idle slightly and see if it comes back. The idle is kicked up slightly when you run the A/C. Just a thought.....

 

I think it has something to do with the idle. Yes the A/C kicks the idle up a little, and I think it happens to kick it up to just the right RPM's to trigger it; but once the noise starts turning the A/C off will not stop it. Also the A/C doesn't need to be on, just seems to happen easier when it is on. It happened to me today just slowly pulling forward from a stop.

 

This symptom follows the IAC. When the A/C compressor engages, the PCM sends a higher voltage to open the IAC, raising the idle speed to compensate for the additional load of the compressor....The IAC is a bypass around the throttle plate.

 

Ok, I figured out what piece is causing this. It is the little black plastic piece on the IAC. It has three parts as seen in this picture. (sorry the picture is blurry, I had one chance before the camera batteries died)

http://i11.photobucket.com/albums/a187/superjfly/Anything%20auto/100_1275.jpg

The filter in that piece must be dirty or something because I can't get it to make the noise when the filter is out.
To make the noise initially all I have to do is start the truck and tap on the plastic part of the intake above the IAC with a wrench and it starts to howl. I can stop the howling by removing the black plastic piece on the IAC. Not sure what the filter is made of or where to get one but I am going to live without it until I can find one. Sure beats buying a new IAC.

 

I am having the same issue. After reading this posting, I am quite confident that the IAC valve is the issue. I've been having problems with the truck idling down, so perhaps the valve has been going out. I'll try replacing it and see what happens.

But, I'm also having a another issue and I'm wondering if the two are connected. A year ago I replaced an O2 sensor. I seem to be having problems with another O2 sensor. I haven't pulled the codes yet, but my suspicion is that its the same one that I replaced a year ago. Could the IAC valve have caused the O2 sensors to fail? Or, could replacing the IAC valve also correct the O2 sensor issue?

Thank you

Daryl Rose

 

I honestly don't think the two are related but I too have an o2 sensor that will throw a CEL for about a week and then it will disappear for half a year. Doesn't usually happen at the same time the IAC is acting up.

FYI: I haven't had an issue with the noise or the IAC since I removed the little filter in the IAC valve.

 

Thanks Superfly, but I think I'm going to replace the whole IAC valve. I've been having problems with it idling down since last winter, so I am going to guess that the whole thing is going bad anyway. I've priced one online with Advanced Auto, runs about $45. I'll call my local AA and see what it will cost me locally. Should be the same, or nearly the same.

It just seems such a coincidence that I've been having problems with this O2 sensor, and IAC at the same time. I looked at my records, and realized that I replaced the O2 sensor in Oct of last year. The O2 started acting up earlier this summer, about the same time the IAC started make the horrible noise. If the two aren't related, then I wonder what’s causing my O2 sensors to go out. I don't think that they should be failing like this. There is a sticky at the top of this forum that said the O2 sensors should last the life of the vehicle. I only have 85K on my truck, and think that I should be able to get more out of these sensors.

Thanks

Daryl Rose

 

Good luck with the IAT sensor and O2 Sensors. If you print out the price online, they should price match it. I do that with Autozone often. I noticed that there prices are different from store to store due to how many competitors are around them. Something to keep in mind.

Neil

 

What code(s) are you getting? A lot of codes that are ostensibly related to the 02 sensors often end up really being caused by problems with the air intake and/or fuel systems.

 

Rockledge,

I haven't had a chance to get the codes pulled, but plan to this week. When I looked up my records from last time, the person who did the reading just simply put down, slow response from O2 sensor, bank 1, sensor 1, so no real codes from that time. But, if I am reading your reply correctly, you are saying that it is possible that the IAC could be in fact causing all of my problems, and that the O2 sensor might be good?

Daryl

 

That's not really what I'm saying, no. What I mean is that, often times 02 sensors get replaced even though they are not the actual problem. For example, based on the description you gave from your records, the previous code sounds like a P0133 (HO2S Sensor Circuit Slow Response Bank 1 Sensor 1). Now, if you look up that code here, you can see from the list of "possible causes" that the code can be caused by several things other than an 02 sensor malfunction.

Post the codes when you get them. Autozone or Advanced Auto will pull them for free.

 

Rockledge,

Stopped by Advance Auto and had them check for codes. There were none. Same story as before. Last time I went to three different parts stores, none could find any codes. I was told by one of them that if the check engine light is not on, then their scanner would not find anything. I finally gave up and paid a mechanic to scan my truck. He was the one who said the O2 sensor was bad. I'll go back to him this weekend and see what he comes up with. I'll mention to him the IAC and see if he feels that could be causing the O2 to indicate that it is bad also.

As I said in my original post, I am confident that the IAC is bad, from the symptoms that I am having, and from what I've read in this and other posting. Also, I looked up what you think might be the previous code, P0133, from that pdf you posted. The very last item under "possible causes" say's: Inlet air leaks. To me, that also points in the direction of the IAC. If the IAC is not bad, then something in that general area is making that horrible noise. The person who originally started this thread said that the noise sounded like it was coming from the air intake and only got louder when he removed the cover. Exact same thing here. However, I did not really realize that hot, humid weather was causing it. The weather has cooled off a bit here, and the noise did go away. So that is another symptom that is on par with the original poster.

Thanks for all of the help and I'll keep you posted and let you know what I find out.

Daryl Rose

 

Just thought that I would update this thread. I finally got some answers to what I thought was an O2 sensor issue.

I had it scanned a couple of times, but no codes were found. I had to take it in to have some other work done. I went to a new mechanic to have the work done. I asked that he have the truck scanned while he was working on it. At first he told me that he couldn't find anything wrong, but a second guy seen something on the print out that he felt could be an issue. The BARO reading was at: 26.9. According to a chart that they have, that setting is for an altitude of 4000 ft, we are only about 1100 ft. He suggested that I clean the MAF sensor.

I had cleaned the MAF sensor a couple of years ago. I thought that there was a sticky at the top of this forum that had instructions to clean the MAF, but I don't see that sticky at this time. Anyone have instructions?

Would anyone suggest try cleaning the MAF again, or should I just replace it? I haven't looked into the cost of a new MAF, but I'm really considering doing just that. That way I know that the issue is solved, and I wont be having this problem anymore.

Thanks.

Daryl

 

Unfortunately, the stickys have been canned (to the dismay of many). This should help you:

https://www.ford-trucks.com/forums/1...-cleaning.html