Go Back   Club Lexus Forums > Lexus Model Forums > SC Models > SC 400/300 > Performance & Maintenance
Sign in using an external account
Register Forgot Password?

Clean your IACV - Idle Air Control Valve

Reply
 
 
 
 
Thread Tools Search this Thread Display Modes
Old 05-27-09, 01:18 AM   #1
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default Clean your IACV - Idle Air Control Valve

I did not plan on making a thread about cleaning the IACV on my 93 sc300 (132k miles), but the results fixed the idle issues I previously had so thought it was worth posting. You may want to consider doing this if you experience some of the symptoms that I have listed below.


Symptoms I Experienced

-After resetting the ECU, the idle would be low and it would take a few drives for the idle to reach normal again.

-At normal operating temperature: Random low idle.

-At normal operating temperature: Low idle then back to normal within seconds or with some throttle.

-At cold operating temperature: Turning the steering wheel at slow or at standstill (when power steering pump is engaged) causes idle to noticeably drop and seems to almost stall.

-At cold operating temperature: Random idle surge while driving within first 2 minutes. Feels like someone is pumping the brakes when you let go of the gas.

Part Numbers

*For 1993 SC300 AT
IACV: 22270-46050
Phillips screw w/ washer: 90079-11030


How to remove IACV on a SC300

I thought it would be a good idea to reset the ECU so I removed both battery terminals before working on the IACV. Removing the IACV is pretty straightforward as it is held down by 2 phillips screws. A problem you may run into is fitting a screwdriver into the bottom screw as the valve cover is in the way. Some kind of angled screwdriver or specific tool could do the trick. I did not have one so I loosened and moved the throttle body just enough for clearance. Also make sure to use a proper fitting screwdriver or bit to avoid stripping the phillips screws as they are on there pretty good. I almost stripped the bottom screw with multiple tools before realizing that I could remove the throttle body.

Once the IACV is removed, you can see if there is any sort of build up on the tip of the sensor. As for mine, it was gunked up with black soot and deposits probably accumulated from over the years. I used some maf cleaner I had laying around to clean off the build-up. Carb cleaner should work as well. I also took the sensor apart for a look inside, but seemed clean so I did not mess with it. Wish I took before and after pics, but again I was not planning on posting.

Before reinstalling, I also removed the intake pipe by the throttle body and sprayed some maf cleaner into the IACV chamber which is the bottom hole as you look into the throttle body. Make sure to put some kind of rag or paper towel to catch all the liquid that flows out where the IACV was installed.

To reinstall just reverse the steps. Reconnect your battery terminals, double check installation, and fire her up. Hopefully this will cure some of your idle woes.


Results

All the symptoms that I listed above are now non-existent in the past week and a half of driving the car. There were no low idle issues after resetting the ECU. There have been no random and strange low idle issues. The cold start idle is also lower at about 1.5k rpms instead of the 1.9-2k rpms it was before. The idle is now nice and smooth. I keep a mpg log so I'll update this to see if it made any kind of difference on the next fill up. In my opinion, this is totally worth the time as the issues often times puzzled and frustrated me.

Update: 07/07/2009
Symptoms have not come back at all. The idle is still smooth!

Also go here for some pics and info of the IACV: http://www.planetsoarer.com/IAC/iac.htm

Tip of the IACV that was cleaned (courtesty of http://www.planetsoarer.com/IAC/iac.htm)
Click the image to open in full size.
This ad is not displayed to registered members.
Register your free account today and become a member on Club Lexus!
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009

Last edited by TheMole; 07-13-09 at 05:42 PM.. Reason: grammar, added info
TheMole is offline   Reply With Quote
Old 05-27-09, 10:34 AM   #2
5sp_jzz30
Lexus Champion
Trader Score: (2)
 
5sp_jzz30's Avatar
 
Join Date: Apr 2007
Location: IL
Posts: 3,562
Default

good post.

i have a similar issue with my car. i was actually planning to do the cleaning today after work.

for those that have a FSM for an sc300 or the NA mk4 supra can look up instruction in the trouble shooting section on how to test the valve and make sure it is actually good. you can clean it all you want but sometimes the part is just bad.
__________________
I build air pumps!

FS: 93 sc300 5spd with extra parts 847-732-7696
5sp_jzz30 is offline   Reply With Quote
Old 05-27-09, 11:43 AM   #3
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Yea that is true that the IACV itself can go bad. Hopefully thats not the case as it is pretty damn expensive for such a small piece. The planetsoarer link in the first post also shows the troubleshooting steps from the fsm.
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 05-27-09, 12:59 PM   #4
YeA 2jZ
Lexus Fanatic
Trader Score: (15)
 
YeA 2jZ's Avatar
 
Join Date: Apr 2005
Location: SC Land, FL
Posts: 5,260
Salty_Kev
Send a message via AIM to YeA 2jZ Send a message via MSN to YeA 2jZ
Default

nice thanks for the write up i have been buggin my tech friend to get this done for me but i guess now i should do it my self
__________________

Slowly modding....
Cardomain Page Please Vote
YeA 2jZ is offline   Reply With Quote
Old 05-28-09, 09:24 AM   #5
xzeus
Rookie
Trader Score: (1)
 
Join Date: May 2009
Location: SoCal
Posts: 99
Send a message via AIM to xzeus
Default

Good writeup. next time take pictures of everything even if you dont think of posting! Such as filling up your gas tank lol jp
xzeus is offline   Reply With Quote
Old 07-07-09, 06:42 AM   #6
lexdud
Pole Position
Trader Score: (0)
 
lexdud's Avatar
 
Join Date: Feb 2008
Location: Fl
Posts: 389
Default

Mole,

How long did it take you to do this job? My SC400 is stalling intermittantly and since the IACV is right there up-front I might try this. Also, how much coolant leaked out when you removed the valve from the block?
__________________
[
lexdud is offline   Reply With Quote
Old 07-07-09, 07:43 AM   #7
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Lexdud,

I previously had to remove the throttle body for a spark plug change on my sc300 so I had some experience. Took me maybe about 30 minutes on my sc300, but it may be different on your sc400. No coolant leaked out as no coolant flows to that area. Again, it may be different on your sc400.

Are you referring to the coolant temperature sensor?
While changing it on the sc300, coolant kept pouring out until I plugged the hole. Reason is because it is mounted horizontally as opposed to vertically on the sc400.

Here are some links:
http://www.clublexus.com/forums/perf...placement.html
http://www.clublexus.com/forums/ls40...ange-pics.html
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 07-07-09, 08:31 AM   #8
YeA 2jZ
Lexus Fanatic
Trader Score: (15)
 
YeA 2jZ's Avatar
 
Join Date: Apr 2005
Location: SC Land, FL
Posts: 5,260
Salty_Kev
Send a message via AIM to YeA 2jZ Send a message via MSN to YeA 2jZ
Default

Hey mole in the pic above what part of the iacv is that exactly ? when i look at mine (still on the tb) it cant imagine how it suppose to look like that ?
__________________

Slowly modding....
Cardomain Page Please Vote
YeA 2jZ is offline   Reply With Quote
Old 07-07-09, 09:07 AM   #9
lexdud
Pole Position
Trader Score: (0)
 
lexdud's Avatar
 
Join Date: Feb 2008
Location: Fl
Posts: 389
Default

Quote:
Originally Posted by TheMole View Post
Lexdud,

I previously had to remove the throttle body for a spark plug change on my sc300 so I had some experience. Took me maybe about 30 minutes on my sc300, but it may be different on your sc400. No coolant leaked out as no coolant flows to that area. Again, it may be different on your sc400.

Are you referring to the coolant temperature sensor?
While changing it on the sc300, coolant kept pouring out until I plugged the hole. Reason is because it is mounted horizontally as opposed to vertically on the sc400.

Here are some links:
http://www.clublexus.com/forums/perf...placement.html
http://www.clublexus.com/forums/ls40...ange-pics.html

Mole,

I was referring to the original link you provided. The author stated that he had removed the entire IACV (housing) and that coolant had escaped when he had. You have an SC3 and an I-6 engine so you may not have had this issue.

I am considering doing this because my SC4 stalled the other day. it runs liek a top and has never given me any problems since I bought it used (it currently has 51K miles). This seems like a relatively east (possible) fix.

Thanks for the info ...
__________________
[
lexdud is offline   Reply With Quote
Old 07-07-09, 09:19 AM   #10
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Quote:
Originally Posted by YeA 2jZ View Post
Hey mole in the pic above what part of the iacv is that exactly ? when i look at mine (still on the tb) it cant imagine how it suppose to look like that ?
The pic is the first post shows the top part disassembled from the base. The part you see when you look at your engine would be the base where the harness plugs into.
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 07-07-09, 09:27 AM   #11
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Quote:
Originally Posted by lexdud View Post
Mole,

I was referring to the original link you provided. The author stated that he had removed the entire IACV (housing) and that coolant had escaped when he had. You have an SC3 and an I-6 engine so you may not have had this issue.

I am considering doing this because my SC4 stalled the other day. it runs liek a top and has never given me any problems since I bought it used (it currently has 51K miles). This seems like a relatively east (possible) fix.

Thanks for the info ...

Ah yea, in that link Peter Scott removed the whole housing on his v8. I only removed the sensor itself via the phillips screws. From the pic, it seems like the screws can be accessed without moving anything on the v8. I would try removing the sensor itself first and cleaning the tip of it before attempting to remove the whole housing.

Your sc400 has such low miles so try the simple stuff first.

What year is it?
Does it stall randomly at any operating/outside temperatures?
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 07-07-09, 09:31 AM   #12
YeA 2jZ
Lexus Fanatic
Trader Score: (15)
 
YeA 2jZ's Avatar
 
Join Date: Apr 2005
Location: SC Land, FL
Posts: 5,260
Salty_Kev
Send a message via AIM to YeA 2jZ Send a message via MSN to YeA 2jZ
Default

Quote:
Originally Posted by TheMole View Post
The pic is the first post shows the top part disassembled from the base. The part you see when you look at your engine would be the base where the harness plugs into.
OiC so when i un screw it and pull it out i can take it apart pretty easily ? I dont want to damage anything in the process
__________________

Slowly modding....
Cardomain Page Please Vote
YeA 2jZ is offline   Reply With Quote
Old 07-07-09, 10:34 AM   #13
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Quote:
Originally Posted by YeA 2jZ View Post
OiC so when i un screw it and pull it out i can take it apart pretty easily ? I dont want to damage anything in the process
Yea I believe it is another 3 phillips screws to disassemble the unit. Mine seemed cleaned inside and moved freely so I just put it back together and cleaned all the gunk off the tip. Good luck with it.
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 07-07-09, 10:37 AM   #14
YeA 2jZ
Lexus Fanatic
Trader Score: (15)
 
YeA 2jZ's Avatar
 
Join Date: Apr 2005
Location: SC Land, FL
Posts: 5,260
Salty_Kev
Send a message via AIM to YeA 2jZ Send a message via MSN to YeA 2jZ
Default

LoL yea u should alwasy clean gunk off the tip LoL... thanks for the info mole i will be doing this asap
__________________

Slowly modding....
Cardomain Page Please Vote
YeA 2jZ is offline   Reply With Quote
Old 07-07-09, 10:42 AM   #15
TheMole
Lexus Champion
Trader Score: (13)
 
TheMole's Avatar
 
Join Date: Oct 2006
Location: SoCal
Posts: 3,437
Send a message via AIM to TheMole
Default

Quote:
Originally Posted by YeA 2jZ View Post
LoL yea u should alwasy clean gunk off the tip LoL... thanks for the info mole i will be doing this asap
LOL yes I concur! Doing so will keep you out of trouble.

Are you experiencing any of the symptoms or just for maintenance?
__________________
Electronic Dance Music Thread
98 Mitsubishi Montero 4wd
05 Scion XB - Sold on 9/27/2014
99 Accord Coupe 5 speed - Sold on 3/28/2013
93 Black Onyx JZS147 - Sold on 9/12/2012
93 Diamond White Pearl JZZ31 - RIP on 09/02/2009
TheMole is offline   Reply With Quote
Old 07-07-09, 10:42 AM
 
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY IACV clean picture write-up tcheung87 RX - First Generation 124 10-04-14 08:16 PM
Guidence on Cleaning the IACV and Throttle Body 1999 ES300 Tjfaz ES300 and ES330 9 03-18-13 05:09 PM
DIY with Pics: Cleaning the IACV-SC400 SC400slide Performance & Maintenance 12 10-07-12 01:11 AM
Cleaned IACV, screeching sound? DrtSwinger Performance & Maintenance 3 05-12-12 01:28 PM
Low idle. Not vaccum leak, not IACV. scENFORCER Performance & Maintenance 31 01-05-12 06:11 PM


Tags
300, 400, air, bad, control, gs, iac, iacv, idle, lexus, low, ls400, rx300, symptoms, valve

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

All times are GMT -7. The time now is 11:49 PM.

Join ClubLexus
Advertising


Copyright © 2000-2008 Internet Brands, Inc. All Rights Reserved
Privacy Policy | Disclaimer | Terms of Use | JOBS


Get all contact info