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Step By Step Instructions For Iacv(idle Air Control Valve)/isc/throttl


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Hello Everyone,

I know IACV has been a huge topic on the forum and I have found various pictures in the RX forum and ES forum on the idle air control valve (IACV) or as others call it the idle speed control valve (ISC). However, I have not found a "step by step" posting to date which definitively shows how to clean this thing so that my car stops giving me idling problems.

Symptoms I have had included:

- low and rough idling that would cause the car engine to start shaking after starting the car

- this eventually got worse to the point that when I start my car, it would not idle unless I gave it gas

- idling problems for me tended to occur more often after my engine was warm or had been sitting in the sun

I hope these series of postings help you fellow LOC members out there. You've certainly helped me in the past so here's my two cents at this common problem. Additionally, the instructions I give are the way in which I have cleaned it myself. As you go about and attempt this, you may find better ways to do so. Please add and refine my instructions/terminology as needed. I am not a professional. I've only changed my oil, air filters, and conducted minor maintenance previously. The bottom line is that if you have the right tools, you should be able to do this. This discovery/ cleaning took me about 2 hours to do cause I ran into problems and there were major steps left out in previous postings that I’ve encountered read. The next time I do this, I believe I can get this done in about an hour or less.

Tools Needed:

1) Tightly fitting Philips Screw Driver

2) Carb cleaner that is O2 sensor safe (I've seen CRC. I used Valvoline Carb Cleaner)

3) Locking Grip Pliers (definitely helped me remove the factory tight screws)

4) Small brush for cleaning

5) Towels for cleaning

6) Pliers (help removed brackets holding the hoses)

7) Latex gloves helps with limit the messiness.

* I used the same gasket and did not replace it. No problems found.

1) Remove the hose that comes from the engine/motor that connects to the air intake hoses.( Hose is below in red – we’ll refer to this as Hose A) When you pull back the rubber hose covering, you will see that a metal bracket is holding the hose pretty tightly in place. Use the pliers to clasps the two metal pieces together to loosen the bracket and pull the hose loose. You can also do this by hand if it’s easier for you.

post-17740-1152411562_thumb.jpg

2) Upon removing the hose, you will want to remove the two air intake hoses. Loosen the three screws above in green and remove the hose. Below is a picture of the intake hoses removed.

post-17740-1152411581_thumb.jpg

3)After removing the intake hoses, I opened the lid to the air filter and moved this to the side of the car to create more working room. I believe there are two clips on the right holding the lid in place. Just pop the two clips and move the cover to the side. I also took out the air filter and temporarily moved this to the side.

post-17740-1152411758_thumb.jpg

4)After removing the intake hose, the throttle body/IACV/black electric coil is revealed. At this point, I removed the black electric wire from the black coil. Once the electric wire is removed you can remove the black coil from the IACV by removing the two screws. Note, the screws are factory tight so use a tight fitting screw driver to remove the screws. One of my screws was partially stripped from the dealership’s work, so I had to resort to my locking grip pliers which helped out tremendously. After removing the two screws, the black electric piece pops right off. When the black electrical coil is removed from the IACV, it exposes a small pencil sized metal stud. You will also notice a washer that sits on this stud. Don’t lose this washer. Take it and put it aside so it doesn’t fall off when you continue on in the next steps.

post-17740-1152412062_thumb.jpg

5)Additionally, I removed the hose coming out of the IACV. We’ll call this Hose B. This hose can be removed in the same manner by clamping the bracket and pulling the hose out. You will see that the hose is removed below. Below are pictures of before and after.

post-17740-1152412087_thumb.jpg

6)Here is where the fun begins. I initially attempted to remove the four screws attached to the IACV at this point, but found that after an hour, this would be nearly impossible to remove considering the location of the screws were in an extremely tight spot. The only way I would be able to remove the IACV is to remove right throttle body. Not as tough as it sounds. Three screws need to be removed to accomplish this. Again, be careful when removing the screws. Also you will see I removed another electric plug and I also cut a tie wrap. Once you complete these steps, the throttle body/ IACV comes out pretty easily. Note when you remove the throttle body, there will be one LAST hose connected to the IACV. Be careful when you remove this hose as radiator fluid may spill. Some of my fluid spilled out so I just refilled my coolant after I was done.

post-17740-1152412207_thumb.jpg

7)Below is a picture of the bottom view of the IACV. You now can EASILY remove the four screws connecting the IACV to the throttle body . In the picture below, I have already removed one of the screws.

post-17740-1152412303_thumb.jpg

Once the four screws are removed the IACV and throttle body separate. Now you can clean both of them with your carb cleaner, brush, towels, cotton swabs etc…. Picture here is before I the cleaning with all the muck inside

post-17740-1152412345_thumb.jpg

Pictures after I cleaned the IACV and throttle body

This last picture is the post throttle body cleaning

post-17740-1152412449_thumb.jpg

post-17740-1152412402_thumb.jpg

post-17740-1152412391_thumb.jpg

8) Once you are done cleaning, just put back the throttle body/iacv the same way you took it off, and put everything back in reverse order. Ensure the gasket is in place. Also, ensure you put the washer back on the electric coil. Make sure you place hose A & B back and ensure the electric plugs are back in their original position. Once these things are in place, then it's all about putting the air filter/hoses back and you are good to go. If you have lost any coolant, make sure you refill it to a safe level.

After completing this cleaning, my car starts up without any problem and idles as if I just purchased the car brand new. Replacing this at a dealership would have costed me $300-400 easily. Let me know if you have any questions. Cheers (Also, I tried to post these as separate replys, but the software combined all my replies into a single reply and did not keep them separated)

*Edited the posting to have the pictures follow step by step in sequential order*

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Hello Everyone, I know IACV has been a huge topic on the forum and I have found various pictures in the RX forum and ES forum on the idle air control valve (IACV) or as others call it the idle speed

Thanks for the write up. Did this on my 131k 99 ES300 this morning. Seems to run perfectly afterwards.

Hmm, you sure it was coolant and not carb cleaner? Anyway, for me that 2 screw were the hardest ones to take out for the first time. The entire process probably closed to the amount of time you put in

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Good intructions, do you have to take off the black metal piece mounted on top on the two throttle inlet holes? What if you strip one of the three phillip screws on the throttle body? I believe they are excessively torqued at the factory...

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Good intructions, do you have to take off the black metal piece mounted on top on the two throttle inlet holes? What if you strip one of the three phillip screws on the throttle body? I believe they are excessively torqued at the factory...

You don't have to take off the black metal piece. Once you remove the three screws holding the throttle body in place (I circled these screws as red in my picture), you just need to grab the throttle body and pull it down and out and it comes out easily. I removed the screws with an electric drill so it was much easier. I actually stripped one of the screws holding the electric coil in place so that is where the locking grip pliers really saved me, otherwise I would have been "screwed"..no pun intended.

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GREAT POSTING!!!! YOU JUST HELPED ME SAVE $620! SHOP WAS GOING TO CHARGE ME $650 (WHICH I CERTAINLY DID NOT HAVE LAYING AROUND) AND I ONLY HAD TO SPEND ABOUT $30 ON TOOLS. THIS POSTING WAS A GODSEND... THANK YOU AGAIN!

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  • 2 weeks later...

GREAT POSTING!!!! YOU JUST HELPED ME SAVE $620! SHOP WAS GOING TO CHARGE ME $650 (WHICH I CERTAINLY DID NOT HAVE LAYING AROUND) AND I ONLY HAD TO SPEND ABOUT $30 ON TOOLS. THIS POSTING WAS A GODSEND... THANK YOU AGAIN!

Anytime! This forum has definitely been very helpful to me so I'm just trying to do my part in return for the members who can use my help. Plus I don't believe in unnecessarily spending hundreds of dollars ($650 in your case) to replace items and parts that don't need to be replaced but simply cleaned. Cheers! :cheers:

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  • 2 weeks later...

Did this cleaning for a friend , car did not run at all , at idle.

OK , managed to do it ,but a few questions :

- The small washer around the pencil size metal stud.Is it wavy? This one was , or is now...

- The idle RPM , what it should be ? At P & D positions.Engine warm. As the owner tried to raise the RPMs by tightening the throttle cable. It did help , but now it was idling way too high.And where is the idle screw ? If there is one...

- How much cleaning is required ? I cleaned allmost everything I could. The rotating piece (?) that comes off , and has these moving flaps , etc etc how much can you clean ? How much MUST you clean ? I managed to use the carbspray as a solvent , so most off the sh.. did come out.Some still remains. Should I worry ?What is the purpose of this "valve" thing? Does it suffer , from this "solvent cleaning abuse" ? It was stuck , when I opened it.Now it moves really freely.

A warning , the screws ARE TIGHT !!! Do not attempt with the wrong size screwdrivers !!!

The instructions are clear , and even I managed to do it ! And the result was impressive.... atleast I am happy myself !!!

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Great directions Golden State. Much better than a manual. My '01 has been starting to idle a little rough in the hot weather lately and sometimes is a bit tough to start--sounds like this could be the culprit. I'll take some time and do this this weekend.

By the way, have you considered changing your timing belt and water pump? I could use some good directions on that, too. :)

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Great directions Golden State. Much better than a manual. My '01 has been starting to idle a little rough in the hot weather lately and sometimes is a bit tough to start--sounds like this could be the culprit. I'll take some time and do this this weekend.

By the way, have you considered changing your timing belt and water pump? I could use some good directions on that, too. :)

Good luck!. Nope, haven't changed my timing belt/water pump yet. I have a little over 70k miles on my ride so things are still looking good.

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  • 4 weeks later...
  • 2 months later...

Your directions and pictures became real handy for my when I did this on my wife's '99 Lexus RX300 over the weekend!

Thanks!

Here are several things I found can improve this DIY.

1. Rather than risk losing the washer that sits on the thing that looks like a pencil (You see it when you remove the black plastic piece), remove the entire throttle unit first.... take it out... then remove the screws to take out the black plastic piece.

2. Use latex gloves to help with the clean up (which I see that you use in your pictures... but I think it's worth mentioning).

3. Instead of cutting the ties that keep the wires together, I opted to use a flat head screw driver to pry out the plastic clip... making it reusable when assembling.

Thanks again!

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Thanks alot for the GREAT INFO!! VERY HANDY

Unfortunately I couldnt get the 3 screws out of the throttle body :( and one of the screws almost got messed up! So instead I sprayed contact cleaner in the small hole leading to the iacv butterfly and kept moving the small wheel that moves the iacv open-close while spraying. It got better but I would have rather took the whole thing and cleaned it well. I used contact cleaner for the electric wire cables and valvoline carb cleaner thats safe on O2 sensors.

The car got alot better, but I still want to get the 3 screws out of the throttle body after i get some tools from sears :D

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  • 2 months later...

By the way, I stripped one of the screws :( I got the screw extractor from sears and used in on 2 of the iacv screws even though only one was stripped. IT WAS PIECE OF CAKE with the sears tool. I think it is alot better than trying the screw driver, worked out great with me unfortunately now I have to get replacement 2 screws but that shouldnt be hard... good luck you all

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  • 1 month later...

GREAT JOB, GoldenStateSilverSport. ThankYou.

I noticed some misspellings (like host instead of hose, loose instead of lose and not instead of note) so I made corrections in the text below...just in case it is still possible to make those corrections in your original post. I am very new to LOC so don't know if that is possible or not.

=========================================================

Hello Everyone,

I know IACV has been a huge topic on the forum and I have found various pictures in the RX forum and ES forum on the idle air control valve (IACV) or as others call it the idle speed control valve (ISC). However, I have not found a "step by step" posting to date which definitively shows how to clean this thing so that my car stops giving me idling problems.

Symptoms I have had included:

- low and rough idling that would cause the car engine to start shaking after starting the car

- this eventually got worse to the point that when I start my car, it would not idle unless I gave it gas

- idling problems for me tended to occur more often after my engine was warm or had been sitting in the sun

I hope these series of postings help you fellow LOC members out there. You've certainly helped me in the past so here's my two cents at this common problem. Additionally, the instructions I give are the way in which I have cleaned it myself. As you go about and attempt this, you may find better ways to do so. Please add and refine my instructions/terminology as needed. I am not a professional. I've only changed my oil, air filters, and conducted minor maintenance previously. The bottom line is that if you have the right tools, you should be able to do this. This discovery/ cleaning took me about 2 hours to do cause I ran into problems and there were major steps left out in previous postings that I’ve encountered read. The next time I do this, I believe I can get this done in about an hour or less.

Tools Needed:

1) Tightly fitting Phillips Screw Driver

2) Carb cleaner that is O2 sensor safe (I've seen CRC. I used Valvoline Carb Cleaner)

3) Locking Grip Pliers (definitely helped me remove the factory tight screws)

4) Small brush for cleaning

5) Towels for cleaning

6) Pliers (help removed brackets holding the hoses)

* I used the same gasket and did not replace it. No problems found.

1) Remove the hose that comes from the engine/motor that connects to the air intake hoses.( Hose is below in red – we’ll refer to this as Hose A) When you pull back the rubber hose covering, you will see that a metal clamp is holding the hose pretty tightly in place. Use the pliers to clasps the two metal pieces together to loosen the clamp and pull the hose loose. You can also do this by hand if it’s easier for you.

2) Upon removing the hose, you will want to remove the two air intake hoses. Loosen the three screws below in green and remove the hose. Below is a picture of the intake hoses removed.

3)After removing the intake hoses, I opened the lid to the air filter and moved this to the side of the car to create more working room. I believe there are two clips on the right holding the lid in place. Just pop the two clips and move the cover to the side. I also took out the air filter and temporarily moved this to the side.

4)After removing the intake hose, the throttle body/IACV/black electric coil is revealed. At this point, I removed the black electric wire from the black coil. Once the electric wire is removed you can remove the black coil from the IACV by removing the two screws. Note - the screws are factory tight so use a tight fitting screw driver to remove the screws. One of my screws was partially stripped from the dealership’s work, so I had to resort to my locking grip pliers which helped out tremendously. After removing the two screws, the black electric piece pops right off. When the black electrical coil is removed from the IACV, it exposes a small pencil sized metal stud. You will also notice a wavy washer that sits on this stud. Don’t lose this washer. Take it and put it aside so it doesn’t fall off when you continue on in the next steps.

5)Additionally, I removed the hose coming out of the IACV. We’ll call this Hose B. This hose can be removed in the same manner by squeezing the clamp and pulling the hose out. You will see that the hose is removed below. Below are pictures of before and after.

6)Here is where the fun begins. I initially attempted to remove the four screws attached to the IACV at this point, but found that after an hour, this would be nearly impossible to remove considering the location of the screws were in an extremely tight spot. The only way I would be able to remove the IACV is to the remove the right throttle body. Not as tough as it sounds. Three screws need to be removed to accomplish this. Again, be careful when removing the screws. Also, you will see I removed another electric plug and I also cut a tie wrap. Once you complete these steps, the throttle body/ IACV comes out pretty easily. Note that when you remove the throttle body, there will be one LAST hose connected to the IACV. Be careful when you remove this hose as radiator fluid may spill. Some of my fluid spilled out so I just refilled my coolant after I was done.

7)Below is a picture of the bottom view of the IACV. You now can EASILY remove the four screws connecting the IACV to the throttle body . In the picture below, I have already removed one of the screws.

Once the four screws are removed the IACV and throttle body separate. Now you can clean both of them with your carb cleaner, brush, towels, cotton swabs etc….

Pictures after I cleaned the IACV and throttle body

This last picture is the post throttle body cleaning

8) Once you are done cleaning, just put back the throttle body/iacv the same way you took it off, and put everything back in reverse order. Ensure the gasket is in place. Also, ensure you put the wavy washer back on the electric coil. Make sure you place hose A & B back and ensure the electric plugs are back in their original position. Once these things are in place, then it's all about putting the air filter/hoses back and you are good to go. If you have lost any coolant, make sure you refill it to a safe level.

After completing this cleaning, my car starts up without any problem and idles as if I just purchased the car brand new. Replacing this at a dealership would have costed me $300-400 easily. Let me know if you have any questions. Cheers (Also, I tried to post these as separate replys, but the software combined all my replies into a single reply and did not keep them separated)

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Thanks again to GoldenStateSilverSport. I am sure your procedure saved me at least $650 considering what dealers here in southern California charge for shop time.

For the benefit of other LOC members who may do this job in the future, I want to share a trick I learned about removing the VERY tight screws (phillips head).

I had tremendous difficulty removing these phillips-head screws (they are all the same size) => the 2 screws holding the coil on the IACV, the 3 screws holding the right throttle body and the 4 screws holding the IACV to the right throttle body. I tried tight-fitting screwdrivers, various phillips tips in a ratchet drive, vise-grips on screwdrivers, etc…but the screws wouldn’t budge. All I was accomplishing was damage to the screw heads.

I was about to give up when I thought of a damaged bolt remover tool (that uses a socket principle) I had seen advertised. My reasoning was that if I could find the correct size remover socket, that the tapered, spiral-flute sockets would fit over and grab the shoulder of the phillips-head screws. Then, I could apply enough torque to loosen them.

I found what I was looking for at Sears. I bought their part number 9-52161 (Craftsman “Bolt-Out”-Damaged Bolt/Nut Remover Set). I also looked at Sears part number 9-52154 (Craftsman “Screw-Out”-Damaged Screw Remover Set) but decided they would do more damage to the phillips heads. Bottom Line…9-52161 did a very nice job. The #4 remover out of this set engaged the shoulder of these particular screw heads well. Note: to drive the remover…I put the hex end of it in an appropriate size socket and used a ratchet wrench to drive the socket.

For those that have not seen them - these remover sockets have tapered spiral flutes inside them, which grab a damaged bolt head when they are turned counter clockwise and release the head when they are turned clockwise.

An afterthought - I was surprised to see these rather large screws in a phillips-head format. Seemed a really poor choice. I have never seen that in an American car…they use hex head instead. Yet, I don’t think this was a mistake because the Japanese designers are smart folks. Therefore, I wonder if the use of phillips-head screws in this application was intentional…to make it that much harder for non-dealer mechanics to work on? The use of these screws make a fairly easy disassembly and cleaning job WAY tougher. It would cause a lot of people to say, "I'll take it to the dealer".

By the way - I did take off the black metal piece mounted on top on the two throttle inlet holes that TunedRX300 asked GoldenStateSilverSport about. It improved access and visibility, which really helped when aligning and bolting up the right throttle body to the left one. I think it made the job easier, overall.

Best wishes to everyone. :D

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  • 1 month later...

Good writeup! Made me clean mine out instead of buying a replacement part.

Dealership had replaced one IAC under warranty. Less than 40k miles later, the hard starts were back! Seems like it needs to be a regular service every 30-40k miles. :( Apparently the air assist hose that feeds the IAC brings a lot of pollution with it.

Since I had the shop manual, I followed it's instructions. I thought about following yours, but the adjustment of the throttle bodies was just another variable I didn't want to deal with. Removing the complete dual throttle body setup is actually not that difficult.

Here are my highlights (assumes you are following service manual steps):

  • Didn't drain the coolant, you will only lose a little when disconnecting the two lines.
  • Service manual didn't mention removing cruise control cable, but you need to.
  • I didn't disconnect the PCV hose, I removed the air cleaner hose with PCV hose attached and let it sit on top of the engine cover.
  • The throttle body mounting bolt is tricky to feel -- but it is directly below the big brass seal.
  • I removed the 2 coolant lines after removing the 3 mounting nuts. You can swing the assembly off the mounting studs, and angle it towards you for better access to the hose clamps.
  • You will need a long socket extension to access 2 / 3 of the mounting nuts. I passed my socket/extension underneath the throttle bodies to remove the bottom most nut.

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  • 3 weeks later...

Thanks for the pictures and detail steps. That helped a lot.

The following is my SHORT CUT:

I got as far as removing the plastic electrical part and removing the washer.

I was having difficulty removing the rest of the philips screws, when I realised that the protuding magnetic shaft rotates a valve and that the root of the problem was that it was sticking. I could feel resistance to turning it.

So I squirted around it liberally with choke cleaner several times until I could feel it rotate easily and return under its own spring power.

Since the main problem was now fixed I decided to reassemble from that point and save myself the harder work.

6 months have passed without any futher problem. I guess my short cut worked without having to remove the vave body.

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Thanks for the pictures and detail steps. That helped a lot.

The following is my SHORT CUT:

I got as far as removing the plastic electrical part and removing the washer.

I was having difficulty removing the rest of the philips screws, when I realised that the protuding magnetic shaft rotates a valve and that the root of the problem was that it was sticking. I could feel resistance to turning it.

So I squirted around it liberally with choke cleaner several times until I could feel it rotate easily and return under its own spring power.

Since the main problem was now fixed I decided to reassemble from that point and save myself the harder work.

I figure the cleaning may have to be done more often but that would be OK since it was quite easy.

Did this today, not "much" trouble, just that my hands and arms seem just a size too big for just about any work on this rig! :lol: . I wanted to say Thanks-a-Bunch to Golden State SS for the excellent instructions and to Geoff1 as well for the short-cut idea. I was all ready to do the whole TB removal, (day-off, all the tools. solvents etc..) Then I saw the short-cut idea and thought Hmm.. about an hour or 3-4 hrs. OK I went for the quick-fix and Presto! All fixed, at least for now. Easy fix (except for the screws) Funny thing is I un-did the right screw first and it came out with pretty modest pressure, I thought "hey, this is gonna be a breeze". Well I finally got the vise-grips to clamp on the other screw and got it out after tearing the hell out of it for 10 min, really soft metal, I was as careful as possible, but I can be a bit ham-handed so I only blame myself. Anyhow I'd recommend a pair of needle nose vise-grips to anyone else doing this. Otherwise the instructions are Prefect! Thanks again!

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  • 1 month later...

We have a 99 RX 300. Ran great and then one day when started it would immediately die. The only way to idle it was to keep my foot on the gas. Saw this post and followed the instructions. One screw on the bottom was hard to bust loose but eventually I got it with the help of some vice grips. Thoroughly cleaned the carbon buildup that caused the moving part to stick and it runs great! A very very helpful post!! Thanks a bunch.

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