guys, i need some help pinpointing the infamous IAC issue. when my truck is idle i hear this "whistle", for lack of a better term. its not real high-pitched, like a teapot; its kinda like when someone tries to whistle, but they try to make a "deep whistle" sound, ya know what i mean? but it only does it at idle (by idle, i mean in PARK sitting still, or in DRIVE with my foot OFF the gas, just rolling.) i think it might be the IAC, but i wanna ask around before i go blow $100 on a new one. is there anyway to test it? (i doubt i can test for it, but i figured id ask.)

any help is appreciated, and, please, if possible, give as many details as possible.

thanks.

if the sound seems to be coming from the air filter, then it's probably the IAC.

Originally posted by Alec
if the sound seems to be coming from the air filter, then it's probably the IAC.

alec, that brings up a good point; where exactly is the IAC located? i dont have my haynes manual here, so i cant check it out. (i never actually popped the hood to listen for it under there, but i will this week.)

also, anyone know of any good places to get an IAC valve cheap? i was just gonna check with napa if i needed one, but i dont know how much theyll charge me - theyre usually pretty reasonable.

thanks

on the OHV the IAC is located on the intake manifold close to the throttle body. It's a cylinder with 2 bolts and a harness.

They aren't as expensive as you think. I replaced mine 2 yrs ago. From the Ford Dealer, at that time it cost $60.24 plus tax. (F5TZ-9F715-B) The gasket (which looks like a figure 8 o-ring) cost an additional $6.96. (95TZ-9F670-AA)

is it the same location and price for the SOHC?

yes.. take off the little shroud thing that says 4.0K SOHC and you'll see it.
i don't know about price

i work as a tech at a ford dealer, and what you are talking about doesn't sound like it would be from the IAC, because i've worked on several sohc explorers and a few windstars that the whistling noise is actually from the plastic intake manifold itself, like a rough edge on the inside is causeing more turbulence and makeing the noise. Don't know why it would just suddenly appears on some of these cars, but they just do, its ford.

theres is a TSB on the SOHC Explorers concering the seperator plate in the auto trans that causes a whistling as well.
not a big deal and doesnt hurt anything although its annoying. The fix is a new seperator plate in the trans.

98-5, Publication Date: MARCH 16, 1998
1997-98 EXPLORER, MOUNTAINEER, RANGER

This TSB article is being republished in its entirety to include one chart to clarify the parts needed for repair.

ISSUE:
A "whistling" or "hissing" noise from the main control area may occur while idling in Drive and/or Reverse on some vehicles that have either a 4R44E or 5R55E transmission. This may be due to an improperly sized orifice hole in the main control separator plate.

ACTION:
Replace the separator plate with a revised separator plate. Refer to the following Service Procedure for details.


SERVICE PROCEDURE

1. Perform normal diagnosis by referring to the appropriate model/year Service or Workshop Manual.

2. Repair all Diagnostic Trouble Codes (DTCs) as listed.

3. Repair all transmission concerns as required.

4. Verify that the whistle/hiss noise still exists. If the condition still exists, install the revised Separator Plate (-7A008-) onto the main control. Refer to the Service Manual for proper procedure. Refer to the following Application Chart for the correct separator plate.

NOTE:
IF A SYMPTOM OTHER THAN "WHISTLING/HISSING" REQUIRES REPLACING THE MAIN CONTROL, REFER TO THE MAIN CONTROL CHART WITH THE UPDATED PART NUMBERS FOR CORRECT APPLICATION.

Originally posted by BajaXplorer
theres is a TSB on the SOHC Explorers concering the seperator plate in the auto trans that causes a whistling as well.


Yes, mine has this so I believe that it applies to any Ex with 4R55E or 5R55E. It doesn't bother me. I noticed that it is not constant, it seems to depend upon temperature. I haven't heard it for awhile.

I don't think that it is the same issue as the IAC problem. I didn't replace my IAC due to humming or any noise problem; mine wasn't maintaining idle speed. I have read other threads on this board where a humming noise is caused by the IAC, so I believe that it is a problem with some explorers. It might be interesting to correlate the type of engine and model year(s) with the humming to see if it is a particular intake setup or if it occurs on all explorers.

tbomb - pop the little black cap off your IAC valve. If the noise goes away then the IAC is the source of your noise. If your idle is fine, you don't need to change your IAC valve unless the noise really bothers you. The black cap is about 1" in diameter mounted to the side of the IAC valve. It takes some effort to get it off. It has a sort of compression fit to it. Once you've taken it off, the next time you take it off is easier. I used some big needle nose pliers to take mine off. I put the pliers between the IAC valve and the black cap and pried outward. It went shooting across my garage once it popped off.

hey, thanks for all the tips guys. ill check it out this weekend when i go back to my moms house and i have a garage and tools ;)

My idle is kinda rough and low (about 550). It has been stalling out on me lately. Sometime it stalls when I shift from reverse to drive or sometimes when I'm driving down the road and just take my foot off the gas. It always starts back up right after. I ordered an IAC valve from my dealer today and it will be in tomorrow. $77.26. Do these symptoms sound like a bad IAC valve?

Originally posted by 98FordX24
My idle is kinda rough and low (about 550). It has been stalling out on me lately. Sometime it stalls when I shift from reverse to drive or sometimes when I'm driving down the road and just take my foot off the gas. It always starts back up right after. I ordered an IAC valve from my dealer today and it will be in tomorrow. $77.26. Do these symptoms sound like a bad IAC valve?

Yes, but it is also possible it could be something else as well. Does it run okay if you open the throttle a little bit to compensate for the IAC not opening? If it does, then it is probably the IAC. If not, then a fuel problem or something else.

I have no complaints when my foot is in the gas, except for it not shifting out of first faster. :D

uh...

What I meant was: when it is idling too slow (550 rpm) can you increase the speed of the engine to normal idle speed (~800) by giving it a little bit of throttle? If so, you are compensating for a non working IAC by letting more air in (what the IAC is supposed to do).

Another way to check is to unplug the connector on the IAC and see if there is a difference. If there is no difference, then it isn't working the way it is supposed to. If the engine dies as soon as you unplug, then it is doing something although it may not be working 100% correct.

Originally posted by dogfriend
uh...

What I meant was: when it is idling too slow (550 rpm) can you increase the speed of the engine to normal idle speed (~800) by giving it a little bit of throttle? If so, you are compensating for a non working IAC by letting more air in (what the IAC is supposed to do).

Another way to check is to unplug the connector on the IAC and see if there is a difference. If there is no difference, then it isn't working the way it is supposed to. If the engine dies as soon as you unplug, then it is doing something although it may not be working 100% correct.

normal idle speed is 800 rpm? whered you hear that? my truck idles at ~600 rpm in park, and drops to ~500-550 in drive (at idle) <-- thats normal, well, for the sohc anyway.

I haven't actually measured the Explorer, cause I haven't needed to. Mine appears to idle at ~800. Usually the idle speed is on the sticker under hood, but not on my truck.

My 89 Ranger idle speed was 750 rpm and I had it on the digital tach lots of times to verify this.

Our 93 Toyota PU idle speed is 700 rpm adjustable.

I've never owned or worked on a vehicle with an idle speed lower than 700 but I suppose it is possible. Usually more difficult to get a smooth idle as the speed decreases.

I'm talking about idle speed in Park or N, not the speed of the engine under load in D.

Originally posted by dogfriend


I've never owned or worked on a vehicle with an idle speed lower than 700 but I suppose it is possible. Usually more difficult to get a smooth idle as the speed decreases.



im asssuming you have the ohv engine? heh, the sohc has anything but a smooth idle ;)

I have to agree with Tbomb. My idle has always been really low.

If you look in the Powertrain Manual (mine is 97) under Typical Diagnostic Reference Values there is a chart titled Measured / PID Values (first chart). The last item on that chart is Engine rpm. Under Hot Idle they give the idle speed as 750 - 830 rpm. It is the same for both OHV and SOHC engines.

On two scans I recently made on my '97 and a friends '98 both were around 650 RPM. The scans though were made within 5 minutes of starting both vehicles. I pulled out a scan I did on mine on 7/30 and with my IAT reading 136F and coolant temp reading 188F, my idle was 771 RPM. I would say 750-830 with the engine up to operating temperature is probably pretty accurate.

hrmm, unless the factory tach is off, i think i might be a lil low then.

any thoughts or suggestions?

Originally posted by tbomb
hrmm, unless the factory tach is off, i think i might be a lil low then.

any thoughts or suggestions?

Check with a scan tool or a digital tach. Generally you check with engine fully warmed up, all accessories (A/C, lights, ect.) off. Trans in Park or Neutral.

Its probably not a big deal if it is a little low, but there could be some other issue that could be causing it to be low including the infamous IAC valve.

Originally posted by dogfriend


Check with a scan tool or a digital tach. Generally you check with engine fully warmed up, all accessories (A/C, lights, ect.) off. Trans in Park or Neutral.

Its probably not a big deal if it is a little low, but there could be some other issue that could be causing it to be low including the infamous IAC valve.

ok, thanks. my truck is going to the body shop/mechanic on friday for 2 weeks for accident repairs, so ill tell them to run a scan and check it out for me. ill post the results.

If it is running at least 650 or so, I wouldn't be concerned about it. When coming up to stop lights, mine reads the same according to my tach. My tach is about 10% lower than my OBD-II scanner though. As long as the engine isn't stumbling or idleing roughly, it is probably OK. If the idle does get too low, it could be symptoms of a failing IAC valve. Mine has already gone throught he "humming" stage in its life. Now that it is loosing its voice, it just yells out every once in a while.

thanks robert. im gonna have a scan run on it while its in the shop for accident repairs and see what they say. if its low, then the first things im doing is replacing the IAC, and then if its still low, i think ill sit in the corner and worry about it :p ;) :confused: ya know, if its not one thing with these trucks, its another, heh.

I put the new IAC valve on tonight and the idle came up. It idles warm around 700-750 and around 650 when in gear. It has not stalled yet but that only happened about once a week so hopefully this fixed that problem. The RPMs dont drop to 200 when I shift from R to D anymore.

When I had that problem, I bought the new IAC but didn't put it on right away. I waited until it started causing a problem again, then took it off in the parking lot and replaced it right there so I would be able to tell if that was the problem (it was).

Well, I'm going to clean the old one and keep it. Apparently these things go bad quickly so maybe I can make it work again if I need it.

The original one lasted 3 years, the replacement has 2 years on it.

On my original one, I could see a shiny area on the shaft where it was rubbing. You can look into the port to see if yours has this.

I think that what was happening on mine was that it was ok when cold but after the engine was warm and the parts of the valve expanded, the shaft started to rub and the valve was sticking mostly closed.

well, i think im gonna get a new IAC and see if it helps, im pretty sure it will after all the stuff ive read about IAC issues.

98fordx24, where did you get your new IAC valve and how much was it?

I got it at Ford for $80. I'm sure you can find it cheaper some place else. Took me all of 2 minutes to put it on. It's idiot-proof.

Originally posted by 98FordX24
I got it at Ford for $80. I'm sure you can find it cheaper some place else. Took me all of 2 minutes to put it on. It's idiot-proof.

alright, cool. ill call a dealership tomorrow and see if they have one in stock; if not, ill have them order it for me.

thanks.

Does the IAC make the voltage meter move up and down? I have the RPM moving up and down but I see it go up and down along with the voltage meter.

The signal sent to the IAC by the computer is a PWM (pulse width modulated) signal. You wont get an accurate reading with a normal voltmeter.

It sounds like yours is trying to control the idle speed by varying the pulse width, but cannot control it for some reason. Maybe a vacuum leak? How much is the rpm moving up and down?

went from 500rpm to 2500rpm. I cleaned my IAC today with some air intake cleaner, said on the back it could be used on IAC and throttle bodies. I sprayed it on held it in for 5 mins then drained for 30 mins.

My god the thing runs so nice now, except that black thing with the filter thingys in it. When I put it on I get the air horn effect. So im riding with it off now and it runs like a dream.

If I run without that black thing though would it do any damage. I tried cleaning the black part and took it apart and cleaned the filters but still not clean. Can I spray some of that cleaner on those suckers?

Thanks dogfriend

Originally posted by MaverickDaKid


If I run without that black thing though would it do any damage. I tried cleaning the black part and took it apart and cleaned the filters but still not clean. Can I spray some of that cleaner on those suckers?


I don't know if the filters can withstand the solvent or not. Try using compressed air to knock the dirt out. You could rinse them in water, and then let them dry out for a while before installing them again.

I don't think that it will hurt to run without the filter for a little while, but I think eventually the inside of the vent passage may get gunked up with dirt if you leave it off for a long time.

I know that this thread is old and that I am reserecting it, but I have a question. After having problems and cleaning my IAC, I seem to now have hesitation in slight acceleration. Could this be caused by the IAC?

I have a feeling it may be a fuel problem. Does the engine need to be at idle for the IAC to work?

-Hank

Make sure the gasket between the IAC and manifold is ok, otherwise you have a vacuum leak which will throw off the fuel/air ratio.

Also, its possible that one of the other sensors (MAF) could be causing your problem.

The main purpose of the IAC is to provide bypass air (bypassing the closed throttle plate) to regulate the idle speed. It also provides the control for "no-touch" starting. Finally, it also acts as a 'dashpot' to prevent the engine from stalling when you suddenly close the throttle.