If your TJ whistled like satan's tea kettle, would you...?

  • Accept it and move on.

    Votes: 1 33.3%
  • Throw a bunch of money at the problem, to try to fix it.

    Votes: 1 33.3%
  • Add a flashing light on the roof, so people really know it's yours!

    Votes: 1 33.3%
  • Sell it on Craigslist.

    Votes: 0 0.0%

  • Total voters
    3
  • Poll closed .

cr0sh

Member
Joined
May 7, 2017
Messages
71
Location
Glendale, AZ, United States
Hi all. Here's the story:

I've only had my 2004 TJ for about a week or so. I purchased it used from a dealer, and overall it runs well. Drove it this morning, all was good. Several days ago, she did something weird: She whistled. Not a small whistle, oh no, but a large all out steam kettle scream. But only while idling.

I started her up to go get a haircut. I left my house, and about a mile down the road, the whistling started - I noticed it when I let my foot off the gas to brake. Accelerating made the whistle go away. But at idle - when braking and stopped - she whistled loudly. I pulled over, opened the hood, and could plainly hear that the whistle seemed to be coming from the throttle body. I felt around the area, probing here and there with my fingers, and it felt like (which at the time I didn't know what part it was, but I learned later) the IAC valve was vibrating with the whistle.

As I sat there probing, the whistle died down, and stopped. I never heard it again the rest of the day. I got my haircut, came back out, started her up, drove her home, and no whistle.

The next day I drove her to work - and the same thing happened. Same order. I parked her, got out - still seemed like the TB/IAC. I tried tightening down the intake hose (from the air filter) - that didn't change anything, and I had no other tools to try anything else. Eventually the sound went away, I went to work, and when I drove home, no issue.

The next time I drove her to work, it happened again, so I stopped at a pep boys and got some TB cleaner and hosed it down on the inside (there was a bit of crud) - I also tried to get it as much as possible into the ports to the IAC. Put it back together, no more noise, and no noise when I came home.

I did some research - everything I read seemed to indicate to clean the throttle body, and IAC valve, etc. I purchased a new TB gasket, and yesterday set to work. I got everything cleaned nice and shiny. When I went to clean the IAC, I decided to do the housing as well. I took it off the TB - and the gasket in between kinda crumbled apart as I separated the pieces. "Aha!" so I thought - likely that gasket was bad. Unfortunately, I didn't have a replacement gasket, but I went ahead and cleaned everything. Then I took the TB and a piece of paper, and "rubbed" with a pencil the outline of the housing opening, and then glued that to a piece of thin cereal box cardboard. I used an x-acto knife and cut out a gasket, then sandwich'd that between the parts, and tightened the housing back on. I then mounted the clean IAC valve (with a new o-ring), and put everything back together. I started her up, she ran well - like normal, maybe a bit better.

Later that evening I went to the store. She ran fine there and back, no noise or anything. This morning I went out to go to a friend's house; on the way there, she started whistling! I stopped in a parking lot, lifted the hood, felt around the TB and IAC - nothing seemed out of place, but the whistling was there. After a few minutes, she quieted down - I drove to my friend's house, we went hiking for a couple of hours, and I drove around - but no more whistling. Before I came home, though, I went to AutoZone and bought a new IAC valve, figuring that might be the next step.

I came home, disconnected the battery (I have a battery disconnect), installed it, and started her up - and I had a high idle - close to 2k RPM. I tried "goosing" the throttle, that only boosted it up to 3k and never went down. I also noticed the CEL on, but I didn't have a code reader handy to check the code. I tried multiple shutdowns and starts - but still the high idle and CEL. I tried to "reset" the computer by touching the positive cable (pulled from the battery) to the negative. Still a high idle and CEL. I disconnected the battery, and came inside to post this small book you are reading.

Ideas? Suggestions? What I plan to try next:

1. Go back out there, and make sure the intake manifold is tightened down properly. Maybe there's a vacuum leak there? If it is a bad intake manifold gasket, that may or may not help - but it's worth a shot; I don't have the time to do anything deep on this engine right now.

2. Then try starting her up, and see if that helped and/or if letting her sit "unplugged" for the last 20 minutes or so has helped anything. I doubt it, but we'll see.

3. I'll try spraying the TB cleaner around the throttle body and gaskets, etc - to see if the idle changes - vacuum leak? Maybe also around the vac lines from the brake booster and PCV (or whatever it is)...

4. If that fails, then I'll chock the wheels, put 'er in gear, and see if adding a load helps anything.

5. If that fails - well, I'll be at a loss. I'll probably try to re-install the old IAC valve and see if that changes anything.

One last thing: I noticed on the new IAC valve that the "pintle shaft" seemed longer than the original IAC valve shaft. The original one had a "sleeve" that could be retracted, but the actual "pintle shaft" couldn't be moved on either one (or so it appeared - I didn't try very hard to move them). The "sleeve" on the new IAC valve didn't move at all, though. To be honest, I can't even see how this valve is supposed to work; it appears that it should be like a valve that moves in and out and "seals" the difference in air between the upper and lower parts of the TB - bypassing the butterfly flap valve. But it doesn't move (like you'd expect a solenoid to move) - unless its some kind of small linear actuator motorized thing?

Ok - if you've read this far, I thank you. I know this has been a very long post, but I wanted to make sure I covered everything I've done or tried - I hope it helps, and I hope someone out there can assist me. Otherwise, she'll probably be taken to my mechanic - I seriously can't stand that damn whistling - of all the things to be "broken" on this vehicle as a used vehicle - I wish it'd happened when I test drove it. But of course, it didn't.
 

UPDATE:


1. New to this - not sure which fasteners were for the intake manifold; the few I could see didn't look easy to get to, and I am sure there are more under the heatshield and elsewhere that I really can't see. I need a new heatshield (and probably those socks too for the injectors; I don't have the heatsoak issue that I know of, but why not fix it before it becomes a problem?). That's all on my list.

2. 20 minute wait didn't help jack - still idling around 1850 rpm - Torque (my "scanner") shows the code as P0505 (Idle Air Control System Malfunction) - duh. No other codes or faults.

3. Sprayed everywhere, no change in idle speed.

4. Put in gear, chocked wheels, put in drive (it's an automatic - forgot to mention that - my bad) - idle came down as it should, but still high - a tad over 1000 rpm (maybe 1050 or 1150?).

5. Well - read on...

So I contemplated re-installing the old IAC valve. I even pulled everything - then I looked at both valves. The look identical - but I did notice a couple of things: On the old valve, the "ears" where the screws pass are "bent" - like it was tightened down with the wrong kind of o-ring or something. It was this way originally, leaving a "gap" between the IAC housing and the IAC valve. I'm not sure if this is part of the issue.

The new IAC valve is "flat" and when mounted, the surfaces mate flat properly, with the o-ring in-between. I also noticed that since running the vehicle, the IAC valve pintle shaft is now longer than it was fresh out of the box. It's not as long as the old IAC valve (that one is out further), but it is longer than what it was before I installed it. So it must've been commanded properly at one time or something to close up the valve (but not enough to reduce idle speed?).

I also found that the connector seemed to fit the original IAC valve better than the old IAC valve - plus, the connector has a busted tab, so it doesn't properly "snap" into place (does anyone know what this connector is called - its a four pin version, I think they are standard style connectors?). On the new IAC valve, it's somewhat loose.

So I decided to keep the old IAC valve in place, and drive it around for a while, and see if the computer re-learns the idle and drops it down properly. I figure that's the next thing to try, even though I really don't have the time for it. I added some zip ties to keep the plug connected and snug (I made sure they weren't interfering with the throttle or anything). After getting everything reconnected, I started it - and still a high idle.
 
UPDATE 2:

Ok - well, I went for a 50+ mile drive; part freeway, a big chunk minor stop-n-go, a few minor hilly areas, a variety of speeds.

When I started, I was again idling with no load at about 1850 rpm or so; once in gear, that dropped to 1500. I drove around the neighborhood a bit to make sure things were safe to continue on a longer drive. One thing I noticed was that on stopping, I could hear a weird noise under the hood (sounded almost like grinding brakes - but I was already mostly stopped) and it felt like a "surge"; but the RPMs didn't change, but it felt like the transmission (again, an automatic) was trying to make me go again. I don't know what this was about, but I kept it in mind and tried to always stop short of people in front of me.

Driving was otherwise normal.

When I got to about 30 miles into the whole excursion, I slowed to make a turn, and as I did so, I heard the whistle again. Except it wasn't as loud, and it warbled a bit - then quickly quieted, and went away (this all took place in about 30 seconds). I never heard this happen again.

I also noticed at the same time that my idle speed had dropped - now it was about 1250 rpm under load (while stopped at a light). By the time I got to 40 miles, it was around 1050 or 1100 rpm under load. It stayed that way for the rest of the drive home. I also noticed that when coming to a stop, the weird "grind" noise wasn't there, nor the surging - or if it was, it wasn't noticeable. When I got home, I pulled into my driveway, and the rpm was still a little above 1000, and when I put it in park, it rev'd up to 1500 rpm. Still much too high, but better than when I started.

So - should I take it to my mechanic first thing tomorrow? Or should I continue to drive it this week (I drive it to work every other day - mon, wed, fri - about 15 miles each way), and see if it gets any better? Or should I do something else that I'm not thinking of? I'm all ears here...thanks!
 
I don't trust ANY sensors or IACs that Autozone sells, I've had too many of them that were bad out of the box. I went to Autozone THREE TIMES one Sunday before they finally gave me an oil pressure sender that worked properly.

Two things come to mind.... the o-ring around the new IAC is defective or the orifice it fits into is dirty and it can't seal. Or the section of the orifice further down into the opening is dirty and not allowing the IAC's plunger to seal properly... maybe like a piece of gunk is restricting the flow and causing the whistle.
 
I don't trust ANY sensors or IACs that Autozone sells, I've had too many of them that were bad out of the box. I went to Autozone THREE TIMES one Sunday before they finally gave me an oil pressure sender that worked properly.

Two things come to mind.... the o-ring around the new IAC is defective or the orifice it fits into is dirty and it can't seal. Or the section of the orifice further down into the opening is dirty and not allowing the IAC's plunger to seal properly... maybe like a piece of gunk is restricting the flow and causing the whistle.

Jerry, thanks for replying - you seem to be a "goto guy" for all things Jeep (and you're really prolific about creating new products - I've ogled many then found your threads announcing betas - so thank you for those things!).

Anyhow - as I noted in my initial post, I spent yesterday cleaning my TB, including the IAC housing. Now, I made a cardboard gasket to replace the one between the housing and the TB - I could see that there might be a leak there - but I did spray the cleaner around the seals as it idled to try to find anywhere there might be a leak - and I didn't notice a change in idle.

I suppose that the IAC could be defective (or the o-ring). Also, when I removed the new IAC I noticed that the pintle shaft length wasn't as long as the original - it had gotten longer (as if commanded to lengthen by the computer) than it was when I put it in, but not as long as the original IAC.

I haven't looked at it since I got home from my long drive; it might have lengthened. Who knows (I didn't measure it, so I really wouldn't be able to tell).

Do you think I should just put in the old one? Because other than the whistle noise, it held idle ok. Perhaps I should also get an actual iAC housing gasket, too, instead of my makeshift one?

Finally - who would you trust for these parts? I usually use AutoZone (it's close by), but I also have Napa, O'Reilly, and Pep Boys close enough. Or, I can order online from RockAuto. Or, if you have a particular Jeep specialist dealer in mind (or I could go to a local Jeep dealer parts dept, if you think that would be best)?

I value your opinion, and thanks again!
 
It's hard to say if the makeshift gasket is air tight or not but it certainly could be. I ran for at least a month with a cooling system thermostat gasket cut out of a cardboard box some military rations (MREs) came in without a leak.

I'd be looking to insure the IAC orifice channel is spotlessly clean like using some TB cleaner with something like a baby bottle nipple brush to get inside to scrub it with.

Also know that the IAC plunger moves in & out as required so that you saw a different length is normal. The PCM will figure where it needs to position it. I'd double-check the o-ring which can cause a heap o' problems if it isn't sealing properly.

You can also clean an IAC (that isn't leaking anywhere) without removing it by simply spraying TB cleaner into the TB while the engine is at idle. The IAC will suck the cleaner in through itself when the engine is idling, but not at higher rpms... it only does anything at idle rpms. The engine will flood and die when you spray TB cleaner at its input slot at idle rpms but that's ok, just restart the engine. That also gives the cleaner more time to work, when the engine dies.

Spray the TB cleaner at the 'idle air control passage inlet' slot when the engine is at idle rpms as shown below. I usually use about 1/3 of the can to clean the IAC and then use the rest of the can of TB cleaner to clean the rest of the TB's interior at higher engine rpms.

TB & TPS Sensor Locations.jpg
 
It's hard to say if the makeshift gasket is air tight or not but it certainly could be. I ran for at least a month with a cooling system thermostat gasket cut out of a cardboard box some military rations (MREs) came in without a leak.

I'd be looking to insure the IAC orifice channel is spotlessly clean like using some TB cleaner with something like a baby bottle nipple brush to get inside to scrub it with.

Also know that the IAC plunger moves in & out as required so that you saw a different length is normal. The PCM will figure where it needs to position it. I'd double-check the o-ring which can cause a heap o' problems if it isn't sealing properly.

You can also clean an IAC (that isn't leaking anywhere) without removing it by simply spraying TB cleaner into the TB while the engine is at idle. The IAC will suck the cleaner in through itself when the engine is idling, but not at higher rpms... it only does anything at idle rpms. The engine will flood and die when you spray TB cleaner at its input slot at idle rpms but that's ok, just restart the engine. That also gives the cleaner more time to work, when the engine dies.

Spray the TB cleaner at the 'idle air control passage inlet' slot when the engine is at idle rpms as shown below. I usually use about 1/3 of the can to clean the IAC and then use the rest of the can of TB cleaner to clean the rest of the TB's interior at higher engine rpms.

View attachment 15913

Jerry, thank you for your response.

My only indication that the gasket is airtight - at least on the outside edges - is the fact that with the old IAC it seemed to work fine and idle at the proper RPMs. I would also assume that the center divider is airtight too, because if it wasn't, it'd probably run higher RPMs. Please note that I haven't disassembled this piece since I put it together (I'm not going there unless I can obtain a real IAC body gasket, or something else seems wrong with it). I also want to note that I put this gasket on dry (no silicone sealant or anything used between the surfaces) - and I did the same on the throttle body gasket as well.

Regarding the cleanliness of the IAC orifice channel - while I can't say I used a baby bottle brush (don't own one - probably should pick one up), I did hose it down with cleaner, and scrub it out with my finger with a cotton shop rag, and made sure there wasn't any lint or anything left behind. That said, my fingers weren't tiny enough to get all the nooks and crannies of the IAC body, but visually the mating surfaces of the orifice and plunger on the old IAC were made spotless and shiny.

Now I want to re-iterate so that you and I are clear here:

1. With the old IAC valve, which I cleaned as spotlessly as I could, my idle was ok - but I had the whistle again for a brief period (a few minutes) this morning. This is what led me to purchasing a new IAC valve, as I had cleaned everything I could yesterday on the throttle body and IAC valve, so I thought maybe the IAC valve was somehow at fault for the whistle.

2. With the new IAC valve, I noticed that before I installed it, the pintle plunger was much shorter than the original - one could say when it was installed, the system was "wide open" - whereas on the old IAC valve, the pintle plunger was so long as to have the system completely shut off, minus a hair or two (maybe a millimeter or so).

3. I currently have the new IAC valve installed, and after my long drive (50+ miles), my idle under load was around 1100 rpm. I have not re-installed the old IAC valve yet; but in the process of deciding whether to re-install it or not, when I had the system back apart, I noticed the new IAC valve plunger had moved out more compared to before I installed it, but it still wasn't as long as the old valve plunger length - and could still be considered "wide open" (the difference was about 1/4 to 1/3 of an inch).

So when you say to spray the cleaner in the oriface at idle (and I am not trying to be contrary or argue with you here - I am just needing some clarification), are you saying with the IAC valve I have currently installed (the new one, with an idle of 1100 rpm), or should I re-install the old one and run the cleaner thru with that?

Again, please note that neither one of these valves looks dirty, nor does the seat in the orifice look dirty, as I had cleaned both yesterday quite thoroughly, with the exception I have already noted about the IAC orifice body. However, I'll concede that maybe running the cleaner thru the orifice might help matters. But again, my question about which IAC I should use is necessary.

Would it be better if I returned back to using the original IAC (and return the new one for a refund)? Or should I try a new o-ring on the new IAC? Or should I return the new IAC and try to exchange it out (until I get lucky)?

I should also note that it isn't likely that this cleaning (or anything else on this matter) will be able to happen tonight, or potentially any time this coming week, due to other matters that take priority for now, which I won't get into. But I do value your suggestions. If you believe that further discussion needs to wait until I can return to the matter, please let me know. Also let me know if you believe running with the new IAC and the higher rpms is a bad thing; if so, then I will take the time to return back to the original IAC.

Thank you again.
 
I dunno what the quality of the current IAC is, I don't trust them when they're from stores like Autozone or O'Reilly's. I'd run the OE Mopar IAC. They don't normally actually go bad, they normally just get dirty and together with the orifice it mounts in simply need to be cleaned to restore things back to good operation.

I'd be inclined to install the OE IAC with a known-good o-ring and an actual gasket.

Again, as explained above, it wouldn't be unusual to see the length of the plunger different in a new IAC vs. one pulled off of the TB. The length of the plunger is changed/varied by the PCM as required to meter the air to produce the correct rpms.
 
I dunno what the quality of the current IAC is, I don't trust them when they're from stores like Autozone or O'Reilly's. I'd run the OE Mopar IAC. They don't normally actually go bad, they normally just get dirty and together with the orifice it mounts in simply need to be cleaned to restore things back to good operation.

Ok - gotcha. Cleaning my TB and the IAC and orifice is what led me to this point (well - ultimately it was that damn whistling; it's so LOUD when it happens). I changed out to the new IAC valve because I thought maybe the whistling had to do with it sticking or something of that matter. After which, I had the high rpms from the new valve...

I'd be inclined to install the OE IAC with a known-good o-ring and an actual gasket.

Ok - I'll swap back to it, hopefully later tonight if I can find the time. Time is my issue right now, due to my other concerns. As far as the actual gasket, I'll have to find someplace that sells them; when I picked up the new IAC from AutoZone, I tried to get the orifice gasket too, but they had nothing in stock - not even at other AutoZones (is this gasket unobtainium?). So for now, I'll run on the cardboard gasket until I can find a real one.

Again, as explained above, it wouldn't be unusual to see the length of the plunger different in a new IAC vs. one pulled off of the TB. The length of the plunger is changed/varied by the PCM as required to meter the air to produce the correct rpms.

That I understand, but right now I am getting the high idle from the new IAC, where the plunger is much shorter (by about 1/4 to 1/3 of an inch) than the old IAC's plunger. It's so short, it could be considered "wide open" as it isn't plugging the orifice at all, whereas the old one almost completely plugged it, as far as I could tell when I mated things up.

Also - another thing I noticed - on the old IAC the "ears" (where the screws mount it to the orifice body) are bent, and it doesn't completely mate to the orifice body - there's a gap; the new IAC valve's ears are not bent, and the whole unit mates tightly, with no gap between. I am wondering if that gap is part of my whistling issue?

Regardless, I'll swap it back. I'll probably get the whistling issue again, but at least my idle won't be high... :rolleyes:
 
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Ok - gotcha. Cleaning my TB and the IAC and orifice is what led me to this point (well - ultimately it was that damn whistling; it's so LOUD when it happens). I changed out to the new IAC valve because I thought maybe the whistling had to do with it sticking or something of that matter. After which, I had the high rpms from the new valve...



Ok - I'll swap back to it, hopefully later tonight if I can find the time. Time is my issue right now, due to my other concerns. As far as the actual gasket, I'll have to find someplace that sells them; when I picked up the new IAC from AutoZone, I tried to get the orifice gasket too, but they had nothing in stock - not even at other AutoZones (is this gasket unobtainium?). So for now, I'll run on the cardboard gasket until I can find a real one.



That I understand, but right now I am getting the high idle from the new IAC, where the plunger is much shorter (by about 1/4 to 1/3 of an inch) than the old IAC's plunger. It's so short, it could be considered "wide open" as it isn't plugging the orifice at all, whereas the old one almost completely plugged it, as far as I could tell when I mated things up.

Also - another thing I noticed - on the old IAC the "ears" (where the screws mount it to the orifice body) are bent, and it doesn't completely mate to the orifice body - there's a gap; the new IAC valve's ears are not bent, and the whole unit mates tightly, with no gap between. I am wondering if that gap is part of my whistling issue?

Regardless, I'll swap it back. I'll probably get the whistling issue again, but at least my idle won't be high... :rolleyes:


You may have a problem other than your IAC valve. I'd go check your intake manifold bolts to see if any are loose, especially towards the rear of the engine. That whistle sounds like a significant vacuum leak, that could also cause high idle speed.
 
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You may have a problem other than your IAC valve. I'd go check your intake manifold bolts to see if any are loose, especially towards the rear of the engine. That whistle sounds like a significant vacuum leak, that could also cause high idle speed.

Thank you for your response.

I agree that checking the intake manifold bolts would be something to do; my problem with that is two-fold:

1. Time - I don't have the time to dedicate to the task, because of other commitments I have (which ultimately won't be finished until August at minimum - the time I have already allocated to this issue ate into the time I should have been working on those other commitments, so now I will have to work extra hard on those in order to meet an upcoming deadline).

2. Heat Shield - I need a new heat shield; I am pretty sure if I pull the existing one in order to get to the various intake manifold bolts, it is going to fall apart. It's a minor thing (I could likely pick one up from someplace if item 1 wasn't an issue).

I do agree that the high idle speed would be explained by a vacuum leak, however, the following would also need explanation (which is why this issue is so damn vexing):

1. Why does this high idle speed only happen with the new IAC valve, but not the original OEM IAC valve? If there were a significant leak due to a loose manifold bolt(s), it should present all the time, regardless of which valve is in place, right?

2. The whistle occurs within a mile of driving after the first startup, when using the original OEM IAC valve, when at idle. It only lasts for a few minutes (but those few minutes are annoying to everyone, and embarrassing to me personally - think about it, bright red TJ whistling like a banshee at a stop light in rush hour traffic - lulz for everyone except the driver), then generally quiets down.

3. The whistle only occurred once with the new IAC valve - and only after about 30 miles or so; it wasn't very loud, it warbled slightly, and was gone fairly soon after (less than a minute of noise).

4. With the original OEM IAC valve in place, my idle speed is fine.

5. With the new IAC valve in place, my idle speed is high.

With this, I personally think I have two problems - depending on which valve is in place:

1. Original OEM IAC valve - whistle on first startup after driving a mile or so, idle speed ok.

2. New IAC valve - whistle after 30 miles (unsure if it will do it again, as I haven't driven it again with this valve), idle speed is high.

...and honestly, I don't absolutely know if what I am referring to as the "original OEM IAC valve" is actually the original valve; I bought this vehicle used, and it had a few owners prior to me. For all I know, one or more of those owners had changed out the original, or none of them did and it really is the original.

So - let's forget the high idle issue - why would the thing whistle on idle, only for a few minutes, and only on the first startup and run of the day, after driving a mile - and then settle down, and not whistle again for the rest of the day (even after having been parked for 8 hours at my work)? A general vac leak wouldn't act like that I would think - it would either be all the time, and/or every time - not just once, for a short time. Also, such a leak would give a high idle - but my idle doesn't change with the whistle. Unless my ears are totally shot, I am almost 100 percent certain that the whistle is coming from the vicinity of the throttle body. It definitely sounds like air - like a steam whistle - not like the squeal of a belt, or a failing bearing, or a mechanical scrape (like brakes can do).

If I could get that one thing fixed, I would be very happy driving this vehicle. Right now, I am anxious when I get in to drive it - I don't know when it will happen, it's always a downer when it does, it's embarrassing, and it's annoying for everyone around me (to give you an idea of how loud it is - once when it happened a semi went by me, and I could hear it loud and clear over that noise - it is loud like you wouldn't believe).

Given all of the above, and my limited time issue - my best bet seems to me to be to swap the IAC valve back out (I've gotten kinda good and quick about it - about a 30 minute job now), and then run the thing over to my mechanic. Hopefully he'll be ok with the warranty I got from the dealer for the vehicle, and hopefully the warranty will cover it. If not, then I'll just have to bite the bullet and pound some more money into the thing. Not what I want to do, given what I paid for it, but what choice do I have...?
 
Thank you for your response.

I agree that checking the intake manifold bolts would be something to do; my problem with that is two-fold:

1. Time - I don't have the time to dedicate to the task, because of other commitments I have (which ultimately won't be finished until August at minimum - the time I have already allocated to this issue ate into the time I should have been working on those other commitments, so now I will have to work extra hard on those in order to meet an upcoming deadline).

2. Heat Shield - I need a new heat shield; I am pretty sure if I pull the existing one in order to get to the various intake manifold bolts, it is going to fall apart. It's a minor thing (I could likely pick one up from someplace if item 1 wasn't an issue).

I do agree that the high idle speed would be explained by a vacuum leak, however, the following would also need explanation (which is why this issue is so damn vexing):

1. Why does this high idle speed only happen with the new IAC valve, but not the original OEM IAC valve? If there were a significant leak due to a loose manifold bolt(s), it should present all the time, regardless of which valve is in place, right?

2. The whistle occurs within a mile of driving after the first startup, when using the original OEM IAC valve, when at idle. It only lasts for a few minutes (but those few minutes are annoying to everyone, and embarrassing to me personally - think about it, bright red TJ whistling like a banshee at a stop light in rush hour traffic - lulz for everyone except the driver), then generally quiets down.

3. The whistle only occurred once with the new IAC valve - and only after about 30 miles or so; it wasn't very loud, it warbled slightly, and was gone fairly soon after (less than a minute of noise).

4. With the original OEM IAC valve in place, my idle speed is fine.

5. With the new IAC valve in place, my idle speed is high.

With this, I personally think I have two problems - depending on which valve is in place:

1. Original OEM IAC valve - whistle on first startup after driving a mile or so, idle speed ok.

2. New IAC valve - whistle after 30 miles (unsure if it will do it again, as I haven't driven it again with this valve), idle speed is high.

...and honestly, I don't absolutely know if what I am referring to as the "original OEM IAC valve" is actually the original valve; I bought this vehicle used, and it had a few owners prior to me. For all I know, one or more of those owners had changed out the original, or none of them did and it really is the original.

So - let's forget the high idle issue - why would the thing whistle on idle, only for a few minutes, and only on the first startup and run of the day, after driving a mile - and then settle down, and not whistle again for the rest of the day (even after having been parked for 8 hours at my work)? A general vac leak wouldn't act like that I would think - it would either be all the time, and/or every time - not just once, for a short time. Also, such a leak would give a high idle - but my idle doesn't change with the whistle. Unless my ears are totally shot, I am almost 100 percent certain that the whistle is coming from the vicinity of the throttle body. It definitely sounds like air - like a steam whistle - not like the squeal of a belt, or a failing bearing, or a mechanical scrape (like brakes can do).

If I could get that one thing fixed, I would be very happy driving this vehicle. Right now, I am anxious when I get in to drive it - I don't know when it will happen, it's always a downer when it does, it's embarrassing, and it's annoying for everyone around me (to give you an idea of how loud it is - once when it happened a semi went by me, and I could hear it loud and clear over that noise - it is loud like you wouldn't believe).

Given all of the above, and my limited time issue - my best bet seems to me to be to swap the IAC valve back out (I've gotten kinda good and quick about it - about a 30 minute job now), and then run the thing over to my mechanic. Hopefully he'll be ok with the warranty I got from the dealer for the vehicle, and hopefully the warranty will cover it. If not, then I'll just have to bite the bullet and pound some more money into the thing. Not what I want to do, given what I paid for it, but what choice do I have...?

This is what loose manifold bolts can sound like. It can be intermittent and change with engine temperature as well :

 
This is what loose manifold bolts can sound like. It can be intermittent and change with engine temperature as well

Well, that definitely sounded similar. I ended up taking my jeep to my mechanic on Wednesday, as I don't have the time to spend working on it. When I drove it in, it happened again, like clockwork - got a mile or so down the road, engine up to temp, then whistling on idle. I got out and checked it again, but I couldn't localize it any better. After a few minutes of idling, it went away. Didn't hear it again all the way to my mechanic.

I let them know what I tried, I let them know all the symptoms. I told them about the manifold bolts, and how I needed a new heatshield and the "socks" for the injectors (not sure what to call that tubing). Gonna have them check the tensioner and other parts as well. Not quite a top-to-bottom, but some basics.

I haven't heard anything back from them yet; if they're trying to isolate the noise, they'll only get one chance per day (at least, that's how I have experienced it). If I had more time, I probably would have tried just letting it sit and idle and see if it just "appeared" without needing to drive it, or if driving is necessary (for some reason). I also would've checked those bolts and changed the heat shield. I also tend to wonder if daytime temperature has any bearing on why I don't hear it the rest of the day (at night right now it is cooler, but it gets up in temperature during most of the day and part of the evening). I wish I had more time to deal with this, but that ain't a thing until after summer.

Ah well - if anyone can figure it out, it will be my mechanic - he's handled all my work for my VehiCROSS, and for the fixes done there on certain issues (plus other work I had him do on my old pickup) - well, his shop has proved its mettle so to speak (he handles everything from oil changes to frame-up restorations - there's been some very interesting vehicles in there from time to time; I'm not a real car guy, but I can appreciate them all the same).

Thanks to everyone for the suggestions and help; I'll update this thread when I know more from my mechanic. I'm sure it's something simple and likely those manifold bolts, and it just comes loose enough at one temp, then stays there a few and goes away as it gets up hotter. It's the most likely explanation, given what I've already tried (and, at least my throttle body and such is clean now, so there's that I guess).

:)
 
I've had this noise from my Throttle spacer because the bolts were not tight enough.

I don't have a spacer, but after removing and replacing my throttle body so many times trying to diagnose this issue, I'm kinda a "pro" at it now! LMAO!

Anyhow - I considered getting a spacer, but I hear conflicting ideas on whether they help matters or not; did you experience anything worthwhile by having one? I've heard they can give a bit better throttle response (not that I've noticed an issue there), and raise your gas mileage somewhat - true? Or is it just a fancy scheme to sell you a fancy piece of metal at a ridiculous price point?
 
I don't have a spacer, but after removing and replacing my throttle body so many times trying to diagnose this issue, I'm kinda a "pro" at it now! LMAO!

Anyhow - I considered getting a spacer, but I hear conflicting ideas on whether they help matters or not; did you experience anything worthwhile by having one? I've heard they can give a bit better throttle response (not that I've noticed an issue there), and raise your gas mileage somewhat - true? Or is it just a fancy scheme to sell you a fancy piece of metal at a ridiculous price point?
What was the outcome? I have a similar IAC issue. Any insight will be GREATLY appreciated.
Thanks.
 
What was the outcome? I have a similar IAC issue. Any insight will be GREATLY appreciated.
Thanks.

I guess I probably should've updated this a while back!

Ultimately what happened was that I got a new manifold gasket, plus heat shield, and heat wrapping on the fuel rail and injectors (that last was to prevent something I read about that is common on the I6, where the heat from the engine can cause whats essentially a "vapor lock" condition with one or more of the injectors - since they were going to have everything apart anyhow, what's a bit more money and time, right?).

They also ended up putting on a new sway bar with disconnects, because I was having a weird "thunk" issue when I turned my wheels going in a driveway; basically the links were interfering with the springs due to the small lift that was on there; likely an issue that had been there since before I bought it. Only downside is now I have to keep the bushings greased well, or they start to "rattle" - so I check up on them at my oil change interval, no biggie.

So they put everything together, and the whistle went away - I thought "Great! Problem solved..."

Nope.

When October rolled around, one day I went to work early in the morning, and it was cold, and sure enough once it got to operating temperature the whistle started right back up! So it was definitely heat/cold related, coupled with the seasons, etc.

I figured I would try to tighten the manifold bolts - the ones that I had read about, the ones up front and the ones in the rear. I ended up having to purchase a few extra bits and bobs (universal joints and extensions for my ratchet); in the end I found I could still only reach the front studs/nuts; I have no idea how you get to the rears. I figured, well, I'll try to tighten 'em up and to hell with it.

I got it up to operating temperature, then hit the nuts/stubs with PB blaster and let it sit a half hour. Then hit it with some more and let it sit (while I was doing this, I think I was also working on my LED signal light conversion - I've wrote about that elsewhere). Then I took my socket and dodads and loosened the nut slightly, sprayed some more blaster on, and then tightened it up, loosen a bit, tighten a bit...

...now, likely it would have been best to use a torque wrench at this point, but I didn't have one handy, so I just tightened 'er up really good, plus an extra 1/8 turn. Probably right on the edge of cracking something, I really don't know. But I'll tell you this:

I haven't had a whistle issue since then, a little over 2 years now.

Ultimately, the IAC, throttle body, etc - had nothing to do with the whistle issue, and I returned the "new" IAC valve and reused the old one (which has also worked fine since). My gasket that I made out of some thin cardboard has held up fine as well.
 
I guess I probably should've updated this a while back!

Ultimately what happened was that I got a new manifold gasket, plus heat shield, and heat wrapping on the fuel rail and injectors (that last was to prevent something I read about that is common on the I6, where the heat from the engine can cause whats essentially a "vapor lock" condition with one or more of the injectors - since they were going to have everything apart anyhow, what's a bit more money and time, right?).

They also ended up putting on a new sway bar with disconnects, because I was having a weird "thunk" issue when I turned my wheels going in a driveway; basically the links were interfering with the springs due to the small lift that was on there; likely an issue that had been there since before I bought it. Only downside is now I have to keep the bushings greased well, or they start to "rattle" - so I check up on them at my oil change interval, no biggie.

So they put everything together, and the whistle went away - I thought "Great! Problem solved..."

Nope.

When October rolled around, one day I went to work early in the morning, and it was cold, and sure enough once it got to operating temperature the whistle started right back up! So it was definitely heat/cold related, coupled with the seasons, etc.

I figured I would try to tighten the manifold bolts - the ones that I had read about, the ones up front and the ones in the rear. I ended up having to purchase a few extra bits and bobs (universal joints and extensions for my ratchet); in the end I found I could still only reach the front studs/nuts; I have no idea how you get to the rears. I figured, well, I'll try to tighten 'em up and to hell with it.

I got it up to operating temperature, then hit the nuts/stubs with PB blaster and let it sit a half hour. Then hit it with some more and let it sit (while I was doing this, I think I was also working on my LED signal light conversion - I've wrote about that elsewhere). Then I took my socket and dodads and loosened the nut slightly, sprayed some more blaster on, and then tightened it up, loosen a bit, tighten a bit...

...now, likely it would have been best to use a torque wrench at this point, but I didn't have one handy, so I just tightened 'er up really good, plus an extra 1/8 turn. Probably right on the edge of cracking something, I really don't know. But I'll tell you this:

I haven't had a whistle issue since then, a little over 2 years now.

Ultimately, the IAC, throttle body, etc - had nothing to do with the whistle issue, and I returned the "new" IAC valve and reused the old one (which has also worked fine since). My gasket that I made out of some thin cardboard has held up fine as well.
So, I take it, by tightening the manifold bolts, it also fixed the high idle?
 
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I'm late to this party...

I've got a high idle problem (on a ZJ) as well which is how I found this thread.

OP mentioned he ordered a new IAC and the plunger seemed longer than the one on the original IAC. One thing I did not realize right away is that the IAC plunger can be manually adjusted. You can rotate it to shorten it, and you should rotate it so it matches the length of your original IAC. Once you install it and start your engine, the idle will be high again, but the PCM will adjust. It will take about a minute and you will see it slowly come down to around 700 RPMs and stay there.

I just joined so I could post this here. I hope it helps someone else.

Meanwhile, my high idle is back ... so perhaps I should not be posting "solutions" just yet :)
 
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