Idle Air Control Valve Purchase

I am experiencing a stalling issue and having read through several threads have come to the conclusion that I need to replace my IAC. What is not mentioned is if it matters the source you get the IAC from.

So, what brand names and or sources are recommended for the IAC?

I'd first try cleaning the IAC. Use a quality throttle body cleaner..being careful not to force/move the needle valve. Works for me.

Thank you for replying but that's not what I am asking. I've gone through with cleaning the throttle body twice. It looks new. I just need to know where to purchase a quality IAC valve.

Doughboyea said:

Thank you for replying but that's not what I am asking. I've gone through with cleaning the throttle body twice. It looks new. I just need to know where to purchase a quality IAC valve.

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I have purchased genuine Mopar parts from We R Mopar www.wermopar.com and been quite happy with their prices and service. I took a quick look at their website and couldn't figure out whether the IAC should be under "intake", "fuel system", or whatever, but you can call them at (855) 935-7900. That would be best anyway because then you will learn what the availability is as well as price.

I always got mine at the local parts store; make sure it has a rubber o-ring, or else you may get air leakage.

I guy the vast majority of engine management sensors DIRECTLY from Jeep.

There is a huge variation in quality/dependability/reliability with engine management sensors.

The extra money you spend on a MOPAR unit is money well spent.

I seriously doubt the IAC causing your jeep to stall. Try starting the jeep, and disconnect the IAC while the idle is at about 700 -800 rpm. Then drive it. If it still stalls, then the problem was NOT the IAC.

People blame the IAC for way too much, as they do not understand its true function, etc....

Issues with wiring, the TPS, O2 sensor, or leaking fuel injectors, or problems with the engine or ignition parts are more likely, that cause an idle miss and or PCM hunting are usually the problem.

A bad IAC, is for the most part the same as a disconnected IAC!!!!

Not sure what year you have. Mine are all 87-90 Renix. I have gotten two good IACs out of 3 at autozone the last 7 years. The bad one had a twisted spring inside, bad right out of the box 2 years ago.

Ecomike said:

I seriously doubt the IAC causing your jeep to stall. Try starting the jeep, and disconnect the IAC while the idle is at about 700 -800 rpm. Then drive it. If it still stalls, then the problem was NOT the IAC.

People blame the IAC for way too much, as they do not understand its true function, etc....

Issues with wiring, the TPS, O2 sensor, or leaking fuel injectors, or problems with the engine or ignition parts are more likely, that cause an idle miss and or PCM hunting are usually the problem.

A bad IAC, is for the most part the same as a disconnected IAC!!!!

Not sure what year you have. Mine are all 87-90 Renix. I have gotten two good IACs out of 3 at autozone the last 7 years. The bad one had a twisted spring inside, bad right out of the box 2 years ago.

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That's true, I guess. I mean, even if it sticks shut, the truck should still at least idle.

bigalpha said:

That's true, I guess. I mean, even if it sticks shut, the truck should still at least idle.

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If the throttle body and IAC valve are clean, the IAC should not close. If it closes, it will kill the engine, by starving it for air. But it will not close by itself, it can only do what the PCM tells it to do. If the PCM makes a mistake based on bad data or failing parts that are causing it to try and control the air fuel mixture by restricting air, it can kill the engine, but is not the IAC's fault!!! It only did what it was told to do. But the more I work on these beasts the more it seems to me that a stalled engine is ignition or fuel problems, or bad sensor data, like the O2 and TPS sensors going bad, or bad wiring to them, or real engine problems.

Even if the IAC closes all the way, shouldn't the idle air control port keep enough air into the engine to keep it running?

Not unless "Uncle Bob" has messed with the throttle stop setting or bypass air setting on the throttle body.

As I recall, closing the air inlet to the IAC port cuts off enough air to kill the engine, unless there is a vacuum leak.

Oh. Well nevermind, lol.

bigalpha said:

Even if the IAC closes all the way, shouldn't the idle air control port keep enough air into the engine to keep it running?

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Cruiser54 can confirm this one way or another. Which ever one of us is right, it still means the IAC by itself can not cause the engine to stall.

OP here. I did not intend this thread to be about diagnosing a stalling issue. I thought I had it pretty much covered and needed to know simply where to go to get one. But, as recommended, I did what was asked.

HappyDog said:

I have purchased genuine Mopar parts from We R Mopar www.wermopar.com and been quite happy with their prices and service. I took a quick look at their website and couldn't figure out whether the IAC should be under "intake", "fuel system", or whatever, but you can call them at (855) 935-7900. That would be best anyway because then you will learn what the availability is as well as price.

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HappyDog, the mentioned site lists the IAC under Fuel System... Fuel Injection for $89.25
WeRMopar.com. Seems decent enough compared to Advanced Auto Parts, assuming it's truly Mopar.

BirchlakeXJ said:

I guy the vast majority of engine management sensors DIRECTLY from Jeep.

There is a huge variation in quality/dependability/reliability with engine management sensors.

The extra money you spend on a MOPAR unit is money well spent.

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I called two local Chrysler/Dodge/Jeep dealers. The closest wanted $119 (retail). The second wanted $150 (beyond retail)! :nono:

So now, at least, I have a source, so thank you HappyDog.



But, for the discussion of stalling diagnosis:

Here is how my 2001 XJ Sport started and drove this morning.

Ambient air at 28degF, cold start:


IAC Valve unplugged, start up:


Notice the rpm's are at most 100 less than when the IAC was plugged in.

IAC Valve unplugged, driving and coming to a stop, at operating temperature:


I'm sure we've all been there:
Customer: Mr. Mechanic, there's this thing happening...
Mechanic: Ok, I'll drive it for a day to replicate the issue...
.....day later.....
Mechanic: I could not replicate the issue.
Customer: But I swear it happens to me!

When at work, the Jeep hovers at stall, usually when warm, sometimes when cold. Today it's been the coldest. After a day in the field driving 5 to 10 miles on local roads and dirt roads, I drive home at highway speeds between 50 and 78 mph. After 30 miles, I am back in my home town with traffic lights and stop signs. The RPM's struggle to maintain 300 rpm at idle but does not usually stall. A couple times in the beginning when this all started during the summer, she stalled after getting home, and that's when I cleaned the IAC. Now when I get home, she doesn't stall, just hovers at stall/run. Recently, in the mornings (but not today, of course :wierd, upon cold start, she would turn on, then stall unless I gave it a little throttle for 30 seconds to a minute. After that, she's back to regular idle around 700 +/- rpm. I am guessing it's the IAC simply based on the improvement from cleaning and assuming the valve becomes stuck periodically in either closed or in the opened position.

So, now what's the consensus?

Did you link the wrong photos? The first two photos show all the gauges dead, and zero?

The third photo shows you at 25 mph, none of which indicate zero mph at a light in drive?

To state it again, the test requires starting the jeep with IAC plugged in, and while it is at about 700 rpm at idle (working correctly, foot OFF the GAS peddle), unplug the IAC, and let it warm up to see if the idle changes up or down if stays at about 700 rpm. Then if the idle is stable, test drive it to see if it still stalls. Also, leave the IAC disconnected, let the engine cool, and see if it starts normally, and idles closer to a normal idle speed from cold to hot.

This statement "Recently, in the mornings (but not today, of course :wierd, upon cold start, she would turn on, then stall unless I gave it a little throttle for 30 seconds to a minute" sounds a bit like the B+ relay failing to reset the IAC at shut down, but it could be a variable vacuum leak or O2 or TPS sensor giving the PCM bad data, or worse a combo of the above.

I would suggest taking it to a parts store and getting a free OBD-II scan, and see if there are any trouble codes pending in the PCM!!! Last time I had stalling it was a dirty cap and rotor (worn and dirty) of all things (in other words ignition parts, in prior years it was a bad temp sensor, bad O2 sensor, and bad TPS....). Is that a check engine light symbol lit up on the third photo?

Also, when you cleaned the IAC, did you re-oil the threads? If not, you need to!!! Also did you move the tip by hand, force it to rotate by hand? If you did, you might have moved the tip on the threads and set it in the wrong place on the threaded shaft, or damaged it.

Ecomike said:

Did you link the wrong photos? The first two photos show all the gages dead, and zero?

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They are thumbnails... click on each for their respective videos.

Ecomike said:

To state it again, the test requires starting the jeep with IAC plugged in, and while it is at about 700 rpm at idle (working correctly), unplug the IAC, and let it warm up to see if the idle changes up or down if stays at about 700 rpm. Then if the idle is stable, test drive it to see if it still stalls. Also, leave the IAC disconnected, let the engine cool, and see if it starts normally, and idles closer to a normal idle speed from cold to hot.

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Ok.. I'll try it that way.

Ecomike said:

This statement "Recently, in the mornings (but not today, of course :wierd, upon cold start, she would turn on, then stall unless I gave it a little throttle for 30 seconds to a minute" sounds a bit like the B+ relay failing to reset the IAC at shut down, but it could be a variable vacuum leak or O2 or TPS sensor giving the PCM bad data, or worse a combo of the above.

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I hate the consistent logic of: ...if not this, then that, if not that then all of above. Troubleshooting is such a pain.

Ecomike said:

I would suggest taking it to a parts store and getting a free OBD-II scan, and see if there are any trouble codes pending in the PCM!!! Last time I had stalling it was a dirty cap and rotor (worn and dirty) of all things.

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I have fuel injection so the cap and rotor wouldn't chime here. I'm going to the store today for some oil filters, I'll ask them to check the scanner.

"Troubleshooting is such a pain." Yes indeed, especially with black boxes!!!!

And this is the one that keeps most from being solved quickly, LOL: "if not that then all of above."

People often overlook how several marginal parts can gang up to make a sometimes it does this problem. How old are the spark plugs? Have you done the simple stuff, like air filter and spark plug checks or replacement? I assume you have but?

LOL, the cap and rotor are on the distributor, and have nothing to do with the fuel injection, LOL. But if yours is a 98-01? with the coil pack, that does not use the rotor and cap or distributor? I was just giving examples of what can causing stalling..... like poor spark quality!!!!

We need to know what year yours is???????? It does make a difference!!!

Looking forward to the scanner post!!!!

Doughboyea said:

They are thumbnails... click on each for their respective videos.



Ok.. I'll try it that way.


I hate the consistent logic of: ...if not this, then that, if not that then all of above. Troubleshooting is such a pain.



I have fuel injection so the cap and rotor wouldn't chime here. I'm going to the store today for some oil filters, I'll ask them to check the scanner.

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OK, third video, the idle jumps way up the last 2 seconds. Was that you giving it gas, or the engine idle climbing up another 400 rpm to about 1300 all on its own with a disconnected IAC?

The check engine light (CEL) came on in the second video, not the first, so disconnecting the IAC MAY have set the CEL. A scan will tell us for sure if that is all there is, or if there are any other lurking pending codes that had not yet set off the CEL.

As stated in a previous post, she's a 2001 XJ Sport.

If you follow the sequence of videos, the first is simply a cold start. The second is with the IAC unplugged. Naturally the computer will sense that there is an issue with the IAC, so the CEL is on. The third video shows the light being on as well and was when I was coming to a stop sign. I stopped the video a second after I had to move. So the spike you saw is unrelated to the idling issue.

Now I just got back from Advanced Autoparts. I drove there after unplugging the IAC while the engine was running, no stalling. The rpm's were similar to video 2. Upon arriving home, the rpm's were lower in the 600 to 700 range. Of course, the IAC is plugged back in and I've driven about 15 miles. The only code on the computer was from the IAC valve being disconnected. Beyond that, all clean. No O2 sensor failures, nothing.

Regarding maintenance, around 64,000 miles, I changed the plugs using Champion branded plugs and an air filter as well. I also torqued the plugs to the required spec... in case you're curious

No more unplugging the IAC while the engine is on. I had the CEL reset at Advanced Auto Parts. As I am due for an emissions check in the next coming week, I do not want to risk failure by having the CEL on only due to my troubleshooting.

OBD-II does not always set codes for a bad TPS that is causing odd, random idle speed issues. The TPS is a wear part, carbon brush variable resistor pot.

When it wears it can give out bad data, that fools the PCM into telling the IAC to cut back the air flow too much, (or increase it thus causing a high idle too) thus causing a stall.

Sticking fuel injectors, can also cause a random idle stall. Also a sticking fuel injector(s) can screw with the O2 sensor data and set off a disturbance that the PCM overcompensates for causing an idle drop (telling the PCM to reduce air flow at idle), ...and so on. If it is not a continuous problem yet, like no IAC connected, then the PCM may not set a pending code or CEL yet. It waits until it has a history of miss fires, or bad data to set a hard code CEL, or pending code (No llight, need a scanner that shows pending codes to detect it). A failing CPS can cause it to stall first, but usually causes a no start pretty soon after that. And a loose wire or connection, dirty battery cables cause stalls...

Also the 2001 is KNOWN for cracked heads that cause issues!!!! The 0331 head is known for cracking and causing miss fires.....

Hard to say with the current data that it is not the IAC, or that it is the IAC. If it were my rig, and I knew I had NOT damaged the IAC cleaning it, I would oil it, and test the TPS and O2 sensor with an analog volt meter and get more data before throwing money and parts at it. Last IAC I bought did not solve the stalling problem. IF I was going to throw parts at it, and I was sure I had not damaged the IAC when I cleaned it, I would go for a new TPS first if the original TPS was still on it!!!