Jeep 4.0L IAC Valve (removed, cleaned & reinstalled)

My 1991 Jeep Wrangler YJ has had idle issues lately so I figured its time to clean the IAC (idle air control valve) again. I cleaned it about 8 years ago and it fixed the same idle issues.
I have driven about 200 miles since cleaning the IAC and it fixed the rough idle.

[@ralphnabozny8494]

I did not know you could expose the spring. Thanks.Now i have something to do

[@DaleClaus]

Sometimes just cleaning will not solve the problem if the unit is bad. I found that one symptom of bad IAC control is that when you are coming to a stop it will feel as if your brake rotors are out of round, this is the IAC pulsating and not moving smoothly. Also, each time that you start the engine the rpms will be different and settle a different place each time, sometimes feels as if a plug is misfiring. Disconnect battery for 30 minutes for ECM to reset, dirve at 40 mph for ECM to reset idle

[@BenjaminLarnerVideo]

subscribed, extremely helpful. Just bought my first jeep 2000 Cherokee classic 4.0 inline six. your videos have been helpful. Thank you.

[@jeepcollector91]

Thanks. Glad this video helped you out. Congratulations on getting your first Jeep. I'm sure you will get decades of enjoyment out of that 4.0L XJ.

[@itsalljustrandom]

Benjamin L congrats on joining the Jeep family! 👍👍

[@BenjaminLarnerVideo]

Thanks!

[@jeepcollector91]

Yeah, the IAC valve can make the Jeep do strange things and like most parts they don't last forever. I have several complete intakes just laying around on a shelf and if a good cleaning doesn't resolve the issues its nice having another IAC valve (and any other part needed) to install for diagnostic purposes to see if it changes anything.

[@svborek]

Did mine last night. Night and day difference.

[@narlonb]

It's the whole shootin' match. Metal dash and pad.

[@suzukirmz250]

You should use maf or throttle body cleaner. Choke cleaner is abrasive for electronics

[@sparky7718]

After you replace the IAC valve with a new one (about $35), let the car idle for about 2-3 minutes. You will hear the car run rough initially, then idle way up, then down to normal. This is the computer reading what is going on and re-adjusting itself.

[@hardliving6931]

sparkymoo Do you have to plug up to a computer after replacing the IAC or will it adjust on its own? Mine started idling high around 1800-2200 RPMs.

[@lostinthedesert3788]

@@hardliving6931 this is a year old so more for people down the road, the jeeps computer will adjust itself just takes a few minutes, maybe a short drive.

[@manuelmarrujo8197]

Good video

[@jeepcollector91]

Sorry I did not show the tools that I used. It was a T20 Torx socket that I used with my short extension and 1/4" ratchet.

[@jeepcollector91]

It will be the same on your ZJ.Throttle body is slightly different.On yours the MAP sensor is mounted on the throttle body,mine is on the firewall.If you are wanting to do a good throttle body cleaning, I would recommend just remove the entire throttle body. You can do a better job cleaning the IAC mounting hole with the throttle body off. Just make sure the gasket between the throttle body & intake is in good condition before reinstalling.The gasket is under $2 if you feel you need a new one.

[@jeepcollector91]

Cleaning the IAC valve doesn't help at all with acceleration issues. It only helps with the idle. Since you are having difficulties removing the bottom screw for the IAC valve I would suggest removing the entire throttle body from the intake (be careful not to damage the seal/gasket if you plan to reuse) and that should make it easier to get that screw out. Also, while the throttle body is removed you can give it a thorough cleaning which may help with any acceleration issues you are having.

[@jeepcollector91]

It has been a while. Are you talking about the dash pad or the entire metal dash assembly?

[@henryvandervoort3796]

Awesome video. Very simple maintenance. Thank you

[@jeepcollector91]

I believe that the fuel pressure regulator is on the top of your fuel pump/sending unit. If you replaced the entire assembly then you must have already replaced it as well. If you just replaced the fuel pump on your original sending unit then most likely you are still running the old fuel pressure regulator. As for the filter, if you don't have an inline filter then I guess all you have is the one on the fuel pump/sending unit. Again, if you replaced the entire assembly then it got replaced also

[@jeepcollector91]

There are several things that could cause that but if you're not throwing codes my first guess would be fuel starvation due to weak fuel pump, bad fuel pressure regulator, or just a dirty fuel filter. Could also be restricted exhaust (clogged cat or muffler) or even dirty injectors. I would start with a good tune up (i.e.: plugs, wires, distributor cap/rotor, air filter, fuel filter, injector cleaner, clean throttle body, and so on…) Its been a couple years since I messed with '96 & up 4.0L's.

[@jeepcollector91]

Remove the steering wheel, remove the gauges, disconnect any wiring attached to the dash, disconnect & remove radio, fold down windshield. remove the bolts that hold the top of the dash (can't remember how many) and the bolts on each side of the dash. I think all of them were torx head bolts. There should be some good write ups with photos on JeepForum that would help. If I remove the dash in my '91 or part out another YJ soon, I will try to make a good step by step video.

[@jeepcollector91]

You could get a fuel pressure gauge and screw it onto the schrader valve on your fuel rail and just make sure that your fuel pressure is where its supposed to be for your year & model Jeep.

[@julienbrunette]

Good God, this really worked. Easy fix and you saved me $100 (parts and labor)! I've been driving around like this for two weeks. Thanks so much!

[@jeepcollector91]

The MSD wires should be good ones but for $81.99 I believe they are selling you the name. You can get a good quality set of Accel 8-mm wires and the cap, rotor, and even the Accel U-groove spark plugs for $76.99 at Advance Auto Parts Part No. TST16. I have never had any problems with them on any Jeeps so far. I used to run Accel on my Nova & Camaro and never any issues.

[@jeepcollector91]

Have you checked fuel pressure or replaced the fuel pressure regulator (on the end of your fuel rail on the '92 XJ)? Mine did the same a while back and also got poor mpg. I replaced the fuel pressure regulator and the power & mpg's came back up to where they should be. Just one bolt and a vacuum line. Only takes about 5 minutes at the most.

[@jeepcollector91]

Mine has always had a slight miss at idle. Several years ago I kept swapping parts (I had plenty of spare sensors, ignition, computer, fuel & intake components) and it was still the same. Checked for vacuum leaks as well. I believe it is a very common issue but I wouldn't worry about it. Had the same slight miss on the last engine as well. Could possibly be a very small exhaust leak pulling cool air into the exhaust resulting in the little pop in the tailpipe that sounds like a slight miss.

[@DaleClaus]

Now you are sounding like my son with at least 3 MAC and 3 Windows laptops, he has found that it is much easier and cheaper to switch parts to find the problem than to have a whole lot of expensive testing equipment. My problem with 2000 Jeep 4 liter w/206k mi. is that after replacing MAP, IAC, TPS and cleaning thottle body, new platinum plugs I still have a little fluttery idle, but everything that I have done has made a big improvement, milage in town has gone from 10 to 14. Maybe o2 sensor?

[@FootageFactory]

Thank you thank you.... you're the man.

[@SuperDagod1]

I just did this to my 2001 xj jeep cherokee. The bottom bolt was tough to get to with all those wires in the way. Mine wasn't as dirty as in the video, probably half as much of the carbon build up. But I sprayed it with carb cleaner and I gotta tell ya, it seems to idle a little bit better than normal. It wasn't bad before but it does seem that it is slightly better. So cool thanks. What else can I do that doesn't cost anything.

[@jeepcollector91]

I also had the low idle problem several years ago and replacing the throttle positioning sensor took care of that issue on mine as well. Sorry I didn't make a video of that. Glad you fixed your Jeep and it's running great again. Thanks.

[@daleclaus7105]

New upstream NKT O2 sensor installed in 2000 Cherokee 4 liter, the Bosch would not fit, hit the bell housing! A 5 mile drive to the NAPA store getting 13.5 mpg, installed the sensor in the parking lot, got 18.5 mpg on the return trip... Oh what a happy boy I am!!! Only time will tell if it also solved the fluttering idle problem??

[@KartKing4ever]

Ah, so that makes sense. The piston is... gone on mine? It's not on the IAC at all haha uh

[@jeepcollector91]

I just sprayed Carb & Choke cleaner into the IAC mounting location then used a rag and my finger to scrub it a little.

[@jeepcollector91]

I did love the simplicity of carburetors until I bought my '91 YJ. The '91-'96 4.0L's fuel injection is about as simple as it gets. Very easy to work on and even if you aren't good at diagnosing the problems you can get a complete intake with the throttle body, fuel rail, and everything still on it really cheap at your local U-Pull then just use it to swap parts over to see what fixes or improves the issue you may have. I have several intakes, fuel pumps, distributors, and coils to do just that.

[@DanielBrown3]

I just replaced mine and it did the trick. I might add that you may need to reset the computer by disconnecting the battery. I got a very high idle speed until I did that.

[@asuservice]

Worked for me ... thanks much

[@christyhansen9342]

thanks for the video

[@rfailing1]

Good post. Will clean this part and see.....My 93 YJ started high idle (1500 rpm) shortly after starting, worsens to 2000 rpm after warming up. This started happening when I got my jeep home after my mechanic did some work on my clutch/hydrolics.....it was not idling high before I took it to him, but this is probably unrelated. Any suggestions?

[@rachealrock3638]

Where can I buy a throttle censor pigtail for a 99 jeep wrangler

[@jeepcollector91]

You can get one from a U-pull salvage yard, local auto parts store, dealer, or ebay... Spent a couple minutes on ebay and came up with this: www.ebay.com/itm/MAP-TPS-Connector-Plug-Harness-Pigtail-Toyota-Mitsubishi-Dodge-Ram-5013998AA/254001015116?fits=Model%3ATJ%7CMake%3AJeep&epid=2297518173&hash=item3b23a3e94c:g:UnkAAOSwmXpb9osa:rk:2:pf:0

[@jeepcollector91]

Here is a MOPAR one but you have to pin it yourself... www.ebay.com/itm/NOS-OEM-Mopar-Throttle-Position-Sensor-Connector-Pigtail-5013999AA/401703992609?fits=Model%3ATJ%7CMake%3AJeep&epid=19021842213&hash=item5d876c7d21:g:N7cAAOSwPYdcXiy6:rk:5:pf:0

[@jeepcollector91]

And if you are needing one for the IAC and not the TPS, I found one of those on ebay as well... Hope this helps. www.ebay.com/itm/4Wire-Harness-Pigtail-Connector-For-Idle-Air-Control-Valve-AC151-Fits-Jeep-4-0L/182627709003?fits=Model%3ATJ%7CMake%3AJeep&epid=22003569741&hash=item2a8575b04b:g:j84AAOSw3h1ZR3Yd:rk:1:pf:0

[@narlonb]

Have you ever removed a YJ dash? If so, do you have any advice, video?

[@rachealrock3638]

What happens when the clip breaks

[@jeepcollector91]

If just the securement clip breaks, you can probably use a zip-tie or two to keep the plug in the socket. I've done that with fuel injector plugs on my Ford E150 cargo van and a few other vehicles in the past with good results. I replied to your other comment with what info I could find for the pigtail for that TPS you mentioned. Whether it is the IAC or TPS you needed the pigtail for, just make sure it matches up with the style plugs your year has. I just did a quick search for those few results but don't know what your year model plugs look like without doing some more research. Been awhile since I messed with any '97 and newer 4.0L wiring harnesses.

[@giniggerbreadman]

mine was also a pain, i used the socket torx heads with an elbow

[@JackE.Johnson322]

i wanna clean my 1995 jeep grand cherokee laredo but i dont know if its safe. Any suggestions?

[@jeepcollector91]

Cleaning the IAC valve shouldn't damage anything on your '95 ZJ 4.0L or 5.2L If yours is having IAC related issues, cleaning it will either fix your issues or it won't. If it doesn't fix the IAC issues then you will most likely need to replace the IAC valve with a new one. I have cleaned several IAC valves on vehicles that weren't having any IAC issues just to do a little preventative maintenance and none have developed any IAC problems as a result of the cleaning. The only way it wouldn't be "safe" is if you were to break/damage anything during removal/installation or if you manage to spray yourself in the eye with the carb cleaner... Hope this answers your question???

[@neutrondata193]

Good morning, I have a 93 Jeep Wrangler and I believe I have an exhaust Valve stuck open on Cylinder 4. I have changed plugs as well as cables and even Injectors. If I unplug that injector it runs fine other than missing that cylinder. However when I plug it in the Fuel gets Blaster out the Exhaust.. Would anyone have a means of loosening that without me tearing it down. BTW it Holds Pressure just fine so my guess is the Exhaust Valve on that cylinder.. TY

[@jeepcollector91]

+Neutron Data Assuming you have confirmed spark on that cylinder and that the injector is indeed firing at the correct timing. Have you pressurized that cylinder with air while on a compression stroke to confirm there is a valve stuck open? Or used a borescope? If it is the valve that is stuck, you may be able to free it so long as it isn't bent though it is somewhat unlikely to be bent on a non-interference engine unless this was a result of hydro-locking or foreign debris finding its way into that cylinder. Could also be a seized lifter or rocker arm which would require some minor tear down. The last time I messed with a stuck valve, I was able to free it by filling the cylinder with PB-Blaster with the piston at the bottom end of the compression stroke and reinstalling the spark plug. Then I rotated the crank by hand with a breaker bar and let the piston push the PB-Blaster through the open valve. I then let it sit overnight with that piston most of the way up keeping the PB around the valve. The next day I backed that piston up some and removed the spark plug. Then completed the compression cycle to clear the PB from the cylinder. I then pressurized the cylinder again and at first the valve was still open but the valve closed within a few seconds and the cylinder held pressure. Not sure if it was a proper method but it worked for me on an engine that had sat for years.

[@neutrondata193]

Jeep thanks for the reply, Yes I have checked for Pressure and it has pressure. I have verified that ALL Injectors are working by moving them around they ALL Stop Dead at that bad Cylinder. I have verified from Disti I am getting fire.. Matter fact I just came in from testing it ALL again... I've never seen anything like this one. I even removed all Injectors and Plugs and started pressurizing in case there was something stuck TO no Avail.. My son whose Jeep it is is questioning my Jeepability and to be honest at this point so am I. My Hummers are not even this confusing LOL.. I'm completely LOST right now in what direction to even go...

[@neutrondata193]

Going to print your post and give that a try.. TY again for the reply... I've spent so much in this thing and just added a new Lift etc... I need to make this one happen for my son..

[@narlonb]

Thank you! That's a real step in the right direction.

[@leonardboudreau8495]

TY

[@adeer179]

Jeep 4.0L IAC Valve (removed, cleaned & reinstalled)

[@dennishill9633]

I had a gas fire on engine melting most vac. Hoses and routing of most. Book says some. I have dislexia. And i get lost if any has the correct 1991 scimatic. Please adive. New carb hook up by passing most smog routing need oem correct. Im limited and need it back to pre fire it was all new passed smog its do in two months HELP PLEASE.

[@jeepcollector91]

Is this on a '91 YJ? How much got burned up?

[@jeepcollector91]

Dennis Hill 1991 Jeep Wrangler YJ 4.0L Vacuum Lines Hope this will help.

[@jeepcollector91]

Dennis Hill Did you get the vacuum lines figured out?

[@dennishill9633]

Still havent attempted yet

[@dennishill9633]

JeepCollector91 back of carb vac to and intake carb and right side of motor

[@leonsemail]

Excellent Video, short, good video and easy to understand. Reduced my RPM's by 2k at idle. Thanks

[@jeepcollector91]

Glad I could help. Thanks.

[@MinnesotaFarmboy]

Did this on mom's car 6 months ago.

[@neutrondata193]

Well it appears the Valve either had Carbon or something else blocking it, we moved the Valves around a bit last night also removed Plug and Injector to blow through as much as possible in both the Intake and Exhaust Valve ports.. Did about everything possible there to no avail. Has anyone ever tried anything that may clean them without my taking the Head off.. I saw this product BUT have never seen nor used it.. Any input is appreciated.. kzbin.info/www/bejne/Y6Ovkn2kosyoj7s if this is a bad idea someone throw a rock so I can start this teardown LOL.. Thanks again for everything...

[@jeepcollector91]

+Neutron Data So you have confirmed that the exhaust valve is indeed staying partially open? If so, I don't think that CRC stuff is going to help your problem since that is used for cleaning cylinders that are compressing and firing which yours is not. (water would have worked nearly the same) You could try the PB-Blaster trick I mentioned before letting the piston hold the PB in place around the valve overnight to see if it would loosen up the debris. When you previously said that fuel comes out the exhaust I kept thinking about injector timing issue; either that injector was firing at the wrong time or some wiring issue or computer issue causing it to fire continuous. But since you had already done a compression check on that cylinder that would eliminate that from the list of possibilities. Would only take a couple hours to pull the head. Or if you didn't want to mess with that engine right now or you were needing it on the road in a hurry, you could always buy a good running used 2.5L on Craigslist for under $400 from someone doing a V8 or 4.0L swap. Can easily swap the engine in a day and tinker with the old engine later.

[@jeepcollector91]

...could also be a busted valve spring. But that would require you to remove the valve cover to confirm.

[@neutrondata193]

JC the Valve Springs all seem pretty solid and clean, and no to be honest I have still not been able to get to the Valve Head to verify it's being stuck open and or even it being bad. I'm kind of stuck between a rock and a hard place at this point. On one hand I know I can remove the Head and find the issue more easily and get it resolved BUT on the other hand if its simply some kind of Carbon Buildup that means I tore the entire head out to clean some Gunk Buildup etc out of it.. Is there ANY Way known to view the Valves bottom without tearing out the head? I know this is a stupid Question as even I tried to think where and HOW that would be possible BUT if I could see that then it would surely make it easier for me. But as I said there is NO way for me to verify with 100% accuracy that the Valve is stuck open etc.. Any Ideas would be appreciated I am trying to keep it simple until it can no longer be simple.. Also I have removed the Valve Cover in the beginning of this all. There are no bad springs rods etc.. Even had it running with the Valve Cover off to very they are all good.. Any Ideas as I said are appreciated..

[@neutrondata193]

Also this Jeep has Sentimental Value to us, so I would like to keep it as Original as possible.. I really like the Straight 6 as they have power and good fuel mileage..

[@jeepcollector91]

+Neutron Data I would verify that the valve is indeed open/leaking before moving any further then. Since you already have the valve cover removed you should be able to tell if the valve is open or sticking. Just remove the rocker arm (make sure the piston is down and out of the way) and use a wooden dowel and a rubber mallet to cycle the valve. (wooden handle on a a hammer works well also then just hit the top of the hammer with your mallet) If it is open then just use the PB-Blaster trick to see if that will free it up from the bottom or spray PB-Blaster on the valve stem and keep cycling it with the dowel and mallet. You can also use a borescope to visually see if the valve is open or damaged.

[@dougharlow6037]

Another question. Will Brake Kleen instead of Carb/choke cleaner work?

[@jeepcollector91]

Doug Harlow It would clean the IAC valve but I am not sure if it will make the piston corrode or anything... I wouldn't spray it in the port that the IAC mounts into. Just spray it on a rag and clean it.

[@videodepository]

NO! Don't use brake cleaner. It will destroy the o-rings.

[@bimmerbent]

I would like to see the movement of travel, that is what is missing

[@jeepcollector91]

I should have wired it up to show movement before and after. I have done it before to see for myself but never thought of filming it. Almost didn't film this video. Most of the IAC valves I have cleaned didn't have enough crud on the shaft to restrict movement but like this one did have enough built up on the tip causing it to bind up and not seat properly while it was still installed. Though I have had a couple that were so nasty that the shaft was gunked up enough to restrict travel. Usually if its that bad I would just replace it since it is a relatively cheap part. Less than $50 for a new IAC for the Jeep 4.0L at most of the big auto parts stores. If you end up replacing the IAC you still need to clean the port that it seats into. If cleaning or replacing doesn't help on yours then I would look into wiring/connector/PCM issues or even intake, throttle body, or vacuum leaks. Sorry that my video lacked the info that you seek. If I get a chance this weekend I will grab one off another intake and make a short video of how it moves. All it really does is pull the shaft part back into the IAC unit which opens the port that the tip seats into and allow the required amount of air pass through the port to keep the engine idling.

[@augustowens711]

Thanks for the walkthrough

[@teddyvision5295]

will this mess up your milage?

[@jeepcollector91]

For mine it just caused a slow and erratic return to idle when letting off the accelerator.

[@Inchonseoul]

I just fixed my daughter's 1999 Rangler's rough idle by fallowing your video cleaned it with carb/ chock cleaner sprayed it all over the valve even unscrewed valve pulled out the spring and cleaned it but didn't touch the port. Thank you so much for putting it on u-tube your video was really invaluable, showing all different angles of the location of the valve, because of that I didn't have much problem finding the part. Thanks again for your excellent video and trouble putting it up on U-tube. Best regards!

[@dougharlow6037]

Did you use air to clean the inside of the tube to remove the gunk? And how or what did you do to clean the other side of the of the IAC?

[@jeepcollector91]

Doug Harlow I have been using "Berryman B-12 Chemtool Carb, Choke, Throttle Body Cleaner" for cleaning the IAC valve as well as for cleaning the port that it mounts into. On the port though, I usually use the B-12 on a clean rag and use my finger and the rag to clean the port.

[@DJ12Ema]

I did this... now my jeep wont start

[@jeepcollector91]

Make sure the connector is plugged in all the way. May check the terminals as well. If the Jeep will start when you depress the accelerator pedal then the IAC is closed completely and may wake up once the engine is started. If it doesn't clear up once started, remove the IAC and make sure the sleeve and spring aren't hanging up and that you didn't accidentally get debris in the port that the IAC mounts into. You can remove the IAC and test it to see if it is operating. I never made a video of testing the IAC but there are several good ones here in KZbin.

[@jeepcollector91]

Did you get the Jeep figured out?

[@giniggerbreadman]

nah my engine quivers a tiny bit when it misses, if you know what i mean, but yea, i have tons of spare parts too, mine is all stock and its getting about 12 mpg with only 140k... ive been trying to track it down for a while, replaced all sensors and ignition, still nothing

[@giniggerbreadman]

mine is having a skip at idle, i just cleaned mine, thanks for the vid, it was very helpful, mine was thickly coated with soot, but i still have a skip, any suggestions? replaced the filter, used injector cleaner, havent touched the pump, '92 xj 4.0

[@giniggerbreadman]

no i have not, but thanks for the tip, im used to carbs, new to all of this electronic crap