Have a 2000 Ranger Super Cab XLT 4X4 with the 4.0L V 6 and automatic. Motor runs strong and performs fine. Even starts fine. Not sure if this is caused by cooler temps, or it just happened to start when our weather changed for the winter. But.... I'll start the truck and take off. Starts fine, runs great. I'll go a few miles and the engine warms up fairly quickly to usually by the time I get 3 or 4 miles up the road I'm warmed up. The first time I stop at a stop sign or light I'll start to hear what sounds like a small dull horn blowing sound. If I have the defrost on and the A/C compressor kicks in, this makes the engine idle go low but it never stalls. When this happens the noise gets louder. If I shut of the ventilation system the noise stays so its not anything to do with the A/C compressor I think its kicking in and lowering the idel has the adverse affect. It used to be that if I tapped the gas the sound would go away and it does not return again that trip. Recently though, I've really had to tap the gas quite a few times and sometimes it does not stop the noise and it gets quite loud. Once I get rolling again it stops and does not come back that trip. What the heck is going on here? I'm thinking of some type of warm/cold air control or throttle control flap or something may be closing too far due to the colder air and when that happens I'm getting this sucking sound that sounds sort of like a sick horn. Any ideas??

 

The fact that it is accompanied by idle problems make me think it is an IAC (idle air control) valve issue. It even seems that the newer 4.0's have issues with the IAC making noises like that. Check for a TSB on the issue, you just might find one.

 

My 96 used to do the same, it was the IAC

 

Ok, so it sounds like I may have the culprit here with the IAC. Do/can I clean and/or repair it or is the only option just replace it? Thanks...

 

well, the one from ford was over 2 hundred(canadian) I think(not sure as it was over three years ago) most aftermarkets were half price, but I found a place that was 68 bucks. But I did try cleaning it first but I guess I screwed it up because shortly after I cleaned it the truck started running very poorly.(idling up and down) So in the end I just put in a aftermarket one and good since then,(knock on wood).

 

Well, after searching for a few hours, I found a thread on a site that had a ton of posts on this subject with a photo to show the location. Could not be easier to get to thats for sure. I had time to look at it yesterday, Sunday. I removed it and was a little suprised to see that it was black inside the ports. I was going to replace it, but many places were closed. I headed down to the AutoZone and got a $2 can of Gumout cleaner and went at it for about 20 minutes using a small test tube cleaner. Its important to use a small screw driver and make sure the metal diaphram piece can move freely back and forth on that rod. Its this hanging up that causes the horn noise when air leaks around it because it cannot seat properly or open properly. This morning it was test time as it was a pretty cold morning in the mid 20's. Not a peep out of it, and the truck actually felt like it was running better. So for now, I think I've fixed it. We'll see how long it lasts, and if it comes back too soon, I'll replace it completely. On this other site they say the Ford OEM one is about $80 where as most aftermarket stores like AutoZone do not carry it, NAPA does and its about $35. Thanks for the tips, saved me some time and cash in exchange for a quiet drive. L8R...