Idle Air Controller (IAC) Valve Test failing (1 Viewer)

[jltemlock]

Hi Everyone:

I'm having trouble with a rough idle when my '93 FZJ80 is in gear. I initially thought it was a bad IAC, so I pulled the sucker out (which is a massive pain) and tried testing the unit by hooking it up to my battery via alligator clips and following the FSM test guide. Low and behold the IAC plunger would not open nor close. The unit would vibrate for a split second when attaching wires to the connectors, but nothing major changed.

So, I bought a new IAC valve and hooked it up to my battery for the test. Low and behold, I had the same behavior on the new valve as I did on the old valve. IE- vVibrate for a second when attaching the wires, but no open/close. I also tested the resistance between the connectors on both units and both are showing 20 ohms- right where they're supposed be.

I have a hard time believing that both the new and old valves are failing in the exact same way, so I'm guessing user error on the test. Does anyone have any guidance on how to test the IAC and/or anything else I could check to determine if the IAC valve is working correctly?

Thanks in advance!

 

[ppc]

The IAC is a "stepper motor". As you go through the test procedure momentarily applying voltage to one of four terminals in sequence the motor rotates (pulses) a very small amount each time. It does not constantly rotate. The movement is better felt than seen therefore the vibration. The rotation will be clockwise or counter clockwise depending on the sequence which terminals 1,2,3,4 or 4,3,2,1 Based upon your description both IAC are working properly.

 

[jltemlock]

Thanks, PPC-

So is there actually no visual indication that it worked correctly? I thought the plunger was supposed to go in/out when open/closed. On mine the plunger doesn't seem to be moving at all.

Thanks again!

 

[ppc]

It rotates on a screw shaft. If you placed a small mark on the edge of the plunger you would see the rotation. It may take 10 or more sequences of touching terminals to make one revolution. i.e. 1, 2, 3, 4, 1, 2, 3, 4 .......

 

[jltemlock]

Thanks so much. I'll go try it right now. Really appreciate the help!

 

[ppc]

Here is a link that has some pictures of the IAC internals.
http://www.lcool.org/technical/80_series/fast_idle/fast_idle.html

 

[Tedward]

Once upon a time I tested an IAC stepper motor. Laid out wires from the iac terminals close to each other, stapled down to piece of wood. Then applied voltage to them by swiping across them quickly with hot wire. Can make the stepper motor move enough see it and can watch it go in either direction.
So lay out and staple down wires from it, then swipe the power across them and should go in/out.
Just adding this little fun project to your thread.

 

[offroadin4fun]

The factory shop manual says to drain coolant before removing it- is that necessary?

 

[Tedward]

No