Anyone know what term(s) for IAC ground?

[TurboJim]

Got my car running yesterday, but IAC doesnt work. I got a 180 target, idle speed is too low, and when I pull out the IAC, its shut (fuly extended)

My only thoughts right now are I am missing a ground somewhere as it worked fine before. Also, are the WB O2's grounds tied into that ground anywhere? My target/actual are ok (13.8) but my old zirconia O2 which I use for my O2 gauge (I use it because I know where it used to read with the stock ECM so I can get close) reads pig rich.

So I think I may have a bad ground out there somewhere. I'll bring my IAC checker home tomorrow to check the circuit, but I tried 2 IAC's and both did the same thing.

Oh, one more thing, anyone ever see erratic info on your data tables? I went to a larger cam so I wanted to pull out some MAP AE, so I did, ok, this is good, I shut it off to see how it starts and every time vac changes I get a gulp of black smoke, I go to the table to recheck and where I edited it MAXED at whatever, 5mS? I pull it back down and close the table and it stuck. So I wonder if its a bad thing to shut the engine off with the table in question in view.... like somehow a spike accidentally edited it...either that or that further supports a bad ground as maybe the digital comm ground is tied in there too?

Any ideas?

 

[bruce]

The aftermarkets don't always use the same IAC strategies as the oems. Some park the IAC closed.

Get an IAC housing, and screw the IAC into it and watch it's behaviour. My $300 Gen VI took a $200 repair to get the IAC driver replaced. Some say it's a common failure item.

The IAC has the power and grounded swapped as the motor moves, in and out, it grounds thur the ecm.

GM uses several grounds for the ecm, one for like the injectors, one for the electronics, one for the O2, etc., etc..

 

[TurboJim]

Right, well, I have an IAC checker made with LED's showing in/out. I;ll just bring it home Tuesday and plug it in to see what its commanding, unless like you say, the fast box is counting 180 closed, but that shouldnt be, it doesnt control idle at all, for now I have the min air screw set to control the idle. Since actual is lower than target, I'd think I'd see the bullseye above the target line, but this isnt the case.

But thanks Bruce for the input.