IAC troubles

[34blazer]

IAC doesn't seem to be operating correctly, actually seems to be shut(extended) and not move at all. Swapped with a known good IAC and same result.
Tested the leads for the IAC;


Key on there is 12v+ at B&D, Blu/Blk strp and Grn/Blk strp

Now it is my understanding that initial key off should reverse polarity, and apply 12v+ to the opposite ports, A&B, but it doesn't.
When I turn the key off, and until complete ECM shut down, 12v is still applied to B&D.
A&B never have any voltage. Something wrong with this picture?
Thanks!

 

[bpman1234]

go to the vortex buick site and read up on the iac great place to start lots of info there .

 

[34blazer]

Yeah Ive been there before, some pretty good info over there. Dont need to know how to adjust the IAC though, or min air setting. Im trying to solve a possible electrical issue, need more in depth information to determine if the driver isnt working properly or if the multiple IACs have failed, or there is a break/short somewhere in the wiring. I have verified the terminated connections are correct.

Thanks!

 

[bpman1234]

what makes you think its your iac how is the car reacting ?

 

[34blazer]

The IAC is fully extended, not metering any airflow. Engine is only running off the min air setting of the throttle blade even though the ECM is commanding IAC counts.

 

[Phoff]

First check your throttle body. Should be .42 at idle. If it's open to much at idle the IAC will remain closed or fully extended.

Pete

 

[34blazer]

Check- less than 450 mV throttle closed

 

[34blazer]

Grounded pins A&B on the ALDL to drive the IAC, as instructed.

OK, so found the Grn/wht wire has a break somewhere. All other leads had ~6v except for that one, ohmed it out and result was infinite resistance.


Great. This should be fun...

 

[TurboBuRick]

Just run a new wire... no?

 

[34blazer]

Mostly likely. Have to take apart the harness to route the new wire correctly, not looking forward to that. But at least I know what is wrong lol

 

[TurboBuRick]

Says who? If you know the circuit is open, just route a wire in just like if were running a gauge and tie it in at the ECM.

That's what I would do.

 

[34blazer]

My OCD wont let me do it that way. LOL

 

[bpman1234]

Funny.

Sent from my LG-MS910 using Tapatalk 2

 

[34blazer]

Found the culprit, the Grn/Wht wire was cut. Just inside the grommet by the ECM.

 

[bpman1234]

glad you got it .

Sent from my LG-MS910 using Tapatalk 2

 

[34blazer]

All fixed! Well sorta. Trans is still cooked as well as the fuel pump, but it starts and idles normally, TF works when I blip the throttle. Fried 2 IACs since only one side of the field was working, found another one in a MPFI TB I had stashed away, glad I kept all those parts from the blazer project. LOL.