R34 GT IACV not getting 12v

[_scott]

Hey All,

My car is idling a bit high when warmed up and seems to be stuck in "cold mode". (bad fuel economy) I noticed when my car is set to ON position, the IACV/AAC valve is getting less than 12v. Seems like there is maybe something wrong with the circuit. 

I'd like to see what happens to the AAC valve when it's getting all 12v when the car is running. I'm a bit of a noob at electrical, how would i go about doing that?

Is it as easy as running a wire from the +ve end of the battery to the +ve end of the valve, and then running another wire from the -ve end of the valve, back to the -ve end of the battery, and then starting the car?

 

I don't really wanna fry anything, so thought i would double check by asking here.

 

Thanks!

[GTSBoy]

Yeah. Don't do this.

IACV power is PWM.

[_scott]

Hmm okay, good think I checked.

@GTSBoy I guess I'll test the circuit the old fashioned way with a multimeter. Ill trace from the ECU to the fuse and then from the fuse to the IACV. Do you know what fuse #14 would be on this diagram? I assume it is the 14th fuse counting from left to right, top to bottom on the kick panel fuse box.

 

 

[GTSBoy]

Nah, that's not how the fuses are identified. If you look, for example, just above fuse 14 on the wiring diagram, you will see the 15A fuse for the fuel pump. That's identified as fuse #1, but it is not the top left fuse in the panel. It's the top right.

Now, I've never thought about which fuse is which by number/order in the panel. Just used the identification of what it does to find it. In this case, it is clearly one of the IGN fuses, so that excludes all the other fuses in the panel. It also directly powers all those other devices, most of which are just pain 12V switched outputs on the ECU. So if you go to the purge solenoid, or the swirl valve solenoid for the inlet manifold switching, you should find 12V there.

You will also find 12V at the IACV, but only if measured direct to ground, not across the solenoid, because the ECU causes the IACV position to be set by PWMing the earth connection through the ECU.

I don't know the R34 fuse box at all. If I had to guess, I'd suggest that you're likely to be looking at one of the fuses labelled "ENG A/T CONTROL". Also, it might be possible that the fuse you're looking for is in the engine bay fuse box, although I wouldn't expect so.