[DIY] How to clean 4age 20v ISCV
Common issue
Idling problem on most 4AGE engine is most probably due to dirty and clog ISCV (Idle Speed Control Valve). By doing a simple cleaning will solved your idling problem. Dirty Throttle Body may also contribute to bad idling due to clog vacumm hole from TB, based on Mr Chin’s page here.
Basic stuffs
ISC system regulates engine idle speed by adjusting the volume of air that is allowed by-pass the closed throttle valve.
1) Stepper motor
2) Rotary solenoid
3) Duty control ACV
4) On-off control VSV
4AGE 20V uses Stepper style, this is 20V ISCV :
Figure A:ISCV side view, top pipe came from air filter hose and bottom pipe out to Air Intake Chamber. The yellowish plastic on the left, there are 2 screw,unscrew it and adjust the idling.
Figure B: Part number , 22270-16030 for Silvertop and 22270-16070 for Blacktop
Location
ISCV located under the TB, right side…here :
picture taken from www.club4ag.com
or here :
original location : 20v-sensors-locations
or you can refer to my friend page, Mr Chin…here.
How to clean it ?
1) Disconnect the wiring connection and 2 hose , one from intake plenum, at the bottom side and the other one from air intake chamber.
here are the hose from air intake chamber, the biggest hose, in the middle of the picture.
2) Once both hose has been disconnected, put a bottle or any container at the bottom hose (from intake plenum side)…it might be cramp a bit, remove the air filter intake hose would make it easier…no hassle for those using velocity stacks… 
once done…spray with carburetor cleaner from the top hose, from air intake chamber…
All the dirty carbon and black particuls came out and fill the container…once satisfied…put everthing in reverse order…remove all tools…start the engine…
wallaa…better idling…
This is what I get after the 1st attempt…wow…!
Then the 2nd attempt…much better…
Good luck and happy DIYing…!
Great site. Love it. Keep it up. I have 1994 AE101 silvertop, Black. Its my baby. I enjoy reading this site. Tanks.
Comment by kevin — May 6, 2008 @ 4:55 pm
wow! thanks for the infos.
though I’m using 16v 4age, this is still beneficial.
keep up!
Comment by driveryg.sivik — August 13, 2008 @ 6:27 am
dear fren, i hv used ur info to clean the iscv and my idling is now better but still i need to adjust the idling, can u provide some info how to adjust it? the 2 side-screw for adjust idling or remove the yellowish plastic cover? tq in advance…
Comment by william — August 14, 2008 @ 12:27 pm
I’d like to know how to determine if the VVT is not functioning?
Comment by patrick cruz — August 28, 2008 @ 6:03 am
sir i have a 20v silvertop engine… when reaching at 6,000 RPM my check engine is coming out…. what could be the cause and how can i resolve the problem.. thank u and more power…. hope you could reply asap
Comment by patrick cruz — August 28, 2008 @ 6:28 am
Patrick,
How detemine VVT functionality…perhaps you can unplug the solenoid connection and see if there any different.
or
Perhaps you can do a small DIY stuff…VVT light indicator, under DIY section.
Regarding the engine light, try to diagnosis…by checking the diagnosis errror code…if any…
Please refer to :
http://www.club4ag.com/technical_main.htm
under “Toyota ECU Diagnostic Codes” section
good luck on your findings…
Comment by Super Admin — August 28, 2008 @ 2:09 pm
im having trouble unbolting the top bolt to get it off to clean….do you have to take off the ITB’s???
Comment by jdmbill — December 30, 2008 @ 9:58 pm
Hi, the pictures you show are for the blacktop. How do I clean the ISCV for the silvertop? When I look on my engine, I do not have that ‘Y’ connector you show in your picture between 1, 2 and E. Instead i just have a single pipe no.2 connecting onto the air chamber. How would I clean the iscv? do I just take the pipe off and spray into air chamber?
Comment by 20vST — September 19, 2009 @ 10:37 am