IAC wire configuration & testing conformation

[jrods2]

GM style 4 wire stepper motor
Wiring- 1 pair of wires closes the valve & 1 pair opens the valve. Which pair closes the valve? (Blue pair or Green pair?) Which is negative & which is positive? If I'm not mistaken. the wire with a white stripe is negative & the wire with the red stripe is positive.
If the GM style is subjected to a 12volt source will it just move one step each time or will it continue to move to the full open position or the full closed position depending on the pair of wires selected?
Reason I'm asking is I don't want to have to remove the wires & swap them from the plug for the IAC motor. I only have 4 pins to use & 1 extra for testing.

[billr]

With those steppers all four wires are used for any movement, either opening or closing. What MS are you going to drive it with? You have pretty much a 50-50 chance of getting it wired "backwards", so having to swap two wires is likely. Don't make connections or insert pins that can't be changed. Applying 12V to either coil, alone, probably won't make the valve even flinch, much less move in a normal manner. I think there is a lot of good info on steppers in the manuals, study there some.

Edit: Oh, yeah... there is no simple +/- polarity for those wires, it is constantly changing as the valve moves.

[gtmdriver]

I wired my GM IACV (the one recommended by Autotune) as shown in the manual.



When I checked it out by wiring it to the connector strips on my JimStim it worked perfectly and calibrated nicely.

[billr]

"the wire with a white stripe is negative & the wire with the red stripe is positive."

I should have asked before... what wires are those? Are those in a pre-made harness? Those probably aren't for a stepper; at least they won't be all that is needed. The GM stepper needs four wires.

[jrods2]

I wired my GM IACV (the one recommended by Autotune) as shown in the manual.



When I checked it out by wiring it to the connector strips on my JimStim it worked perfectly and calibrated nicely.

Thanks for the info.

[jrods2]

With those steppers all four wires are used for any movement, either opening or closing. What MS are you going to drive it with? You have pretty much a 50-50 chance of getting it wired "backwards", so having to swap two wires is likely. Don't make connections or insert pins that can't be changed. Applying 12V to either coil, alone, probably won't make the valve even flinch, much less move in a normal manner. I think there is a lot of good info on steppers in the manuals, study there some.

Edit: Oh, yeah... there is no simple +/- polarity for those wires, it is constantly changing as the valve moves.

1st. I have a MS2 with a prewired harness.
2nd. First line of post is GM4wire stepper
3rd 4 wires. 2 blue(blue/wht & blue/red) 2 green(grn/wht & grn/red) I know from the manuals that these wires change polarity on a constant basis. in Tuner studio I see that the IAC can be set up.
4th. What do you mean that there is no simple +/- polarity for these wires?
5th. I can apply 12 volts to either pair of wires & I do get a step. I haven't set up an indicator to measure the amount of the step but now I will, by measuring the step I can also determine the direction of the plunger on the stepper motor. If I know which set of wires moves the plunger I will know which wires will move it in or out to control idle.
6th. I'm going to plumb the 4 wires by the diagram for a GM 4 wire stepper(it is a Autotune stepper). If its not right I'll buy more pins and change the wires.(I DIDN'T want to have to go thru the process of recutting the wires and moving them to a different pin).
Thanks for the info, it is helpful.

[nismoautoxr]

There are 2 different style stepper IACs from GM. The early square screw in type that actually threads into the throttle body . This was mostly pre 1993 TBI and PFI. The later stuff is the 4 in a row in the figure . As Bill says . The wires are constantly changing polarity. I have a test noid that plugs in for testing purposes...its hard to describew until you see it in action. The only times I have seen polarity (wiring)issues is with Jeep throttle bodys. The GM is as the manual has it wired. I have done 3 of these and own 1 right now (LS1 swap 240sx). You just need to follow the manual and you should be ok but be prepared for a little hassle getting all the tuning stuff like you like it . It is a bit of a challenge until you get a little bit of practice under your belt setting them up. As far as swapping wires around...I understand your point on the repin because the terminals snap in from the component end of the connector so you are cutting and splicing the wires at that point rather than a simple repin into the connector body. I was able to follow the manual and it worked fine on my LS1. That is the only help I can really offer.

[billr]

Okay, that was my mistake about the red/wht stripes; I just was thinking blu and grn, and some other wires with stripes. If you apply 12V to a coil it may flinch and feel like a step, but may not be a proper full-step. More important, the direction it seems to move is irrelevant. Direction must be determined using the full four-wire stepping sequence. You can't determine direction by just energizing one coil. Do that and wire it up and you may find it works fine and (wrongly) conclude I am full of BS. Or, it may be backwards and you will get frustrated and (again, wrongly) conclude that steppers are flaky or too complicated to use. That 50-50 chance... If you don't want to de-pin, and I sure understand that, then make a temporary harness for just the MS/IAC connection. Loose DB-type pins/sockets are economical and convenient for this type of testing.

[jrods2]

good advice thank you for the help, I know its not really that complicated, I just wanted to avoid the repin issue. the sujestion about a temp harness is the ticket. thanks guys.