TOPIC: IAC Winter Bypass Module

For those of you who have to deal with the Harshness of winter, ie: where it's really freakin' cold, here is a little mod I put together for just such an occassion.





The valve gets wired in via a switch to a power source that requires the key on. You don't want this draining the battery.

It can also be done much simpler with a smaller valve but this is what I threw together.

If your engine has a hose feeding the IAC then it can be applied and there may be other ways to ge the same results depending on the engine.

Karl Fortner
Tacoma, Washington

Bravo, Dr.Karl!

Too bad more engines don't use a hose to feed filtered air to the IAC. So easy to work with!

12v DC Normally Closed (when power is off)inline hose valves can be found on charcoal canisters in some vehicles. I found one on a Range Rover in the junkyard.

If an engine has a closed off manifold vacuum port, another way to do this is to get a suitable 12V DC hose valve, and hook the valve to the vac. port via some hose. On other side of the valve you connect a small filter (a fuel filter?). Wire it thru a switch to a key-switched fused 12 V power source. If the hose size is, say 3/8"ID, you could "tune" the amount of extra air(and the increased idle speed) by restricting the ID. Use plastic hose adaptors down to a smaller hose ID, or use a manual valve inline.

If you have already restricted the IAC air feed in the TB, this setup gives you an on-demand fast idle speed--IT's manual, no modulation, just on/off. With port FI,the manifold is "dry" so less concern about the port's position in the manifold?

If the PCV vacuum port is capped for the re-route, how about using that port??

Anyone else got any ideas here?

TracyG Gadgetman Reno

After thinking about this some more, I took the valve apart and found that the 1/8" hole could be placed in the valve itself.

In the "OFF" / closed state the 1/8" hole is the breather, in the "ON" / open state the valve opens up supplying an unregulated flow of air to the IAC.




Basically the tubing runs from the IAC to the valve "out" port and a fresh air line from the Air Intake Plenum to the "IN" port on the valve.

and it works just fine.

Karl Fortner
Tacoma, Washington

Hi Tracy,

"If the PCV vacuum port is capped for the re-route, how about using that port?? "

Good point, very easy to tap into that port to add fresh air to assist the IAC.

Karl Fortner
Tacoma, Washington