This tutorial will go over how to replace the mechanical Idle Air Control Valve (IACV) on the AW11 with an electronic one that works much more consistently!
- Electronic Vacuum Switch Valve (VSV)
- Illuminated Toggle Switch
- Fifteen Feet of 18 Gauge Red and Black Wire
- Valve Stem Cap
- 12 Volt Battery or an AC to DC Converter
- 12 Volt Relay Timer
- Automotive Fuse Holder
- Automotive Fuse (10 – 20 Amp)
Note: I used a VSV from an SW20 that I ordered off of eBay. The illuminated toggle switch you can find online, but I grabbed one from AutoZone, along with the wire. The valve stem cap I took off of my old bicycle.
NEW NOTE FROM AUTHOR (April 4th, 2018): Now that I know a bit more about working with electrical, I’d highly recommend using an automotive relay between the switch and the relay timer. This prevents high loads from destroying the switch. I plan on updating this article eventually when I try this again.
In this tutorial I am going to be installing my switch and relay timer in the center console tower, which sits between the driver and passenger seats.
Before starting this project I highly recommend planning what kind of switch you want (square, round, etc.), where you want the switch to be installed, and whether or not you want to have a relay timer to automatically shut off the VSV for you.
It’s not required that you use a relay timer, but it certainly makes it easier for you so you don’t have to remember to switch it off when driving.
1. Remove the intake up to the the throttle body:
2. Locate the hole in the throttle body that is managed by the IACV:
3. Press the valve stem cap into the hole to plug it up:
4. Cut about 6 – 10 feet of red and black wire. Crimp some connectors onto the ends of each one. Connect them both to the VSV:
5. Mount the VSV anywhere that makes sense to you:
Note: I replaced my air filter some time ago with a “warm air intake”, and had one of the original air filter mounting brackets to use
6. Pull the wires through the firewall behind the battery into the cabin:
7. Cut another 4 – 6 feet of red and black wire. Remove your stereo / head unit. Splice the red wire to the red power supply line going to the head unit; and splice the black wire to the black negative / ground line going to the head unit:
This will ensure that the VSV only draws electricity when the car is on.
8. Remove the center console tower (two screws on each side, and two screws inside the compartment on top), and run the spliced wires up through the center console so that they are accessible where the tower will be.
9. Cut or drill holes in the center console tower for the toggle switch and the wires that will be used for the relay timer:
Note: I had round switches so I used a stepped drill bit to drill out the holes I needed. The hole on the right is the one that will be used for this project. The switch on the left is already being used by my undercarriage lights.
10. Place the switch into the center console tower:
11. Place the relay timer into the center console tower and wire it up with the toggle switch:
- The red (positive) wire from the head unit should have a fuse spliced in (I used a 20 amp fuse) and then connect directly to the Power pin on the toggle switch.
- The black (negative) wire from the head unit should split into three wires:
- One goes to the ground pin on the toggle switch.
- Another goes to the DC- port on the relay timer.
- The last one connects to the black (negative) wire on the VSV.
- The Accessory / Load pin on the toggle switch should make a Y-split to the COM and DC+ ports on the relay timer.
- The red (positive) wire from the VSV should connect directly to the NO port on the relay timer.
12. Tidy up the wires and tuck them where necessary:
13. Connect one side of the VSV with the farthest port on the right of the IACV:
14. Connect the other side of the VSV to the intake with a barb fitting:
Or if you still have the stock air intake, connect it to the big side of the Y-fitting:
15. Program the relay timer using a battery (or AC to DC converter) and the Electric Timer Relay Manual. Set it to use “Function 02” and to close the relay after 180 seconds (3 minutes).
Note: You can set the relay to be on / open for as long or as short as you’d like, but three minutes seems to be about the right amount of time the car needs to warm up in normal driving conditions.
16. Turn on the toggle switch and turn on the car:
If all goes well, the car should start up fine and idle around 1500-2000 RPMs. Then when the timer reaches 0, the relay should close and the idle should drop down to around 800-1000 RPMs.
I’ve noticed this has improved my gas mileage; mainly because the old IACV I had would only intermittently work, and most of the time I idled high. Another benefit is I no longer have to hear the motor die for a moment when the idle goes above 1600 RPMs at a stop and the ECU cuts the spark momentarily to drop the idle back down.
If for whatever reason you no longer want to use this mod, just remove the valve stem cap from the IACV hole in the throttle body and bridge the two hoses going to the VSV together.
The original idea for this project came from Paul Woods of MR2OC.CO.UK:
Screenshots of Sources
These are screenshots of the original articles from Paul Woods, mirrored here for posterity: