The idle air control stepper motor which is a GM part does not respond at all. I don't know how to trouble shoot the circuit or the part. I read, and re-read what I could find in the Mega Manual, but I come up empty.

I removed the motor from the housing and let it hang inside the car window still hooked up and watched it and felt it as I turned things on and off, and no response. It does not buzz, click whir, hum, or get warm. I have tried it with the engine running, and with the engine off. I have switched the coil leads around various ways as per the manual and still nothing.

I am not sure what I am looking for. Does anybody know how to check the IAC motor itself? I have posted on the MS website and hope to get some insight there, but was hoping one or two of the brilliant slanters would know something here.

Even after reading the manual multiple times, in multiple places, I am not sure what kind of signal this thing gets from the ECU. I don't know what kind of current I am looking for from the ECM. And I don't know what conditions would trigger movement in the motor. What can I change that will produce a response? What electronic levers can I pull at one end to see if there is movement at the other?

This is not a critical thing. It runs fine. But the IAC provides better starting, and cold start drivabity. For now I am back to the fidle valve I wired in.

As always, thanks in advance.

Sam

_________________

If thats the IAC we played with in May its suspect.

Try another one....Id use a V6 one if possible.

I have about 9 V8 ones under the work bench.......

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Sandy, Do you have a known good one or two you would sell? I know they are cheap, but I am feeling like a bit of a tight wad these days. I have spent a ton of money on the car lately, and have a few big budget items to try and procure on a small budget. If you do, name your price for S&H etc. and I will send a check.

Is it true that when you twist on the pintel it should extend or retract. I cannot get this one to do so. Maybe I am not twisting enough times. However, the coil wires do show 50 ohms each, which I suspect is about right. So they should be trying to do their job if they get the right input.


From what I understand, if you put 12 volts to one of the coils, it will spin all the way one way or the other. I have not tried this with mine yet. I am told you can spin the pintel right out of there, in which case you just thread it back in. I am told. The coil wire pairs are the wires of the same color. The two blue ones are on the side with the connector clamp, and the two green ones are on the side away from it.

Sam

_________________

Sam
Connecting the 12V to a coil directly is sound advice. This will prove whether the IAC motor is good or not. At that point you should be able to replace it or look at the wiring/signal from the ECU.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Thanks Frank. I will do that. Sandy, I realized you said look for a v-6 IAC, however, the MS program for IAC is fully programable. Which means I may never get it to work. But if I can figure it out, I can make any motor fill the bill. Thanks guys.

Sam

_________________

Yes, it should.

Not really - it just spins a few degrees and stops. This link explains how they work:

http://www.taomc.com/bits2bots/stepmotor.htm

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Testing stepper IAC movement in any meaningful way will require electronics. Applying a steady 12v to any of the coils won't do much if anything. Specific waveforms must be applied to the coils with accurate timing between the two to get the pintle to extend or retract.

The pintle will only go out so far then stop. If the pintle is over-extended it must be pushed in physically or else the electronics will have no affect. Moving the pintle by hand takes a decent amount of force, an easy push may not move it. If it is hooked up to an active driver, the electronics could be applying a "braking" signal making moving it very difficult by hand. Likewise when retracting there is a limit to where it won't retract any further.

The wiring is somewhat critical - if either of the pairs is reversed (or worse, crossed) it may not move, or move in the opposite direction as intended. Also with regards to the MS - when switching between a simple valve and stepper you have to change the MS programming options otherwise the IAC chip will stay turned off. I think this may have changed in recent firmware, but I recall the MS only using the IAC for warmup, not active idle control. There was one table that said something like at 100 deg, it is open 15 steps. At 120deg, open 10 steps, etc. If this table is left empty, even with IAC turned on it won't move.

In a quiet environment you may be able to hear it moving if you have sharp hearing. Under the hood? no way with the engine running. If you grab it you may be able to feel the pulses. Each single step is very small, less then a 1/16". So unless the electronics are commanding it to move continuously you will unlikely see it moving either.

I actually built a micro-controller based device to test these. Two buttons, one to extend one to retract with each button press sending two or four pulses, I forget. I could let you borrow it if you wanted to pay for shipping Sam.

More details about the waveforms and movment here.

Pierre, To move the pintle by hand do you simply push/pull straight in, or push and twist. I know there are several different types used by GM.. This one has a round stem, and 4 wires. Some had a square stem, and six wires. Thanks for your info. I am slowly accumulating bits and pieces of the full picture here.


I have two of these. One spins freely, and the other does not spin at all. It seems one must be wrong. They are from roughly the same year Buicks, one NA V-6 and one turbo V-6.

Thanks for the offer of the testing device. It might be cheaper in the long run to simply purchase a new IAC than to pay shipping both ways, especially if the test shows the old part to be bad anyway.

Thanks for the link, Matt.

Sam

_________________

Sam, I guess it's hard to quantify "spins freely". My point was it shouldn't be super easy to move/spin - it should easily carry its own weight if you stood it on the pintle even when not plugged in.

This IAC stepper motor has a round shaft, but has a keyed slot in it, that prevents it from turning. When I apply 12 volts to one of the coils I feel and hear a slight movment either out, or in, depending upon the last movement and the polarity of the leads. For instance, if I hold the pintle between my fingers and touch the leads to B+ and ground, it will move in or out a very minute amount, and stop. Then if I reverse the leads, it moves the same amount back the other way, and stops. This seems logical as to what I have read about them. Pierre, do you think it is possible that both of these motors have mechanical binds in them? I cannot push or pull, or turn either of these units in or out. They are where they are.

If I install the IAC body on the TB and hook it up, it starts up and idles at 2K RPM and nothing I do seems to bring it down. There is a calibration process that is written in the Manual, but what it says does not make sense to me in light of the parts I have here, and how they behave. I will read all of this again a few times.

I am not sure the outputs of S1-S4 are doing anything meaningful to the stepper motors. And, I don't know how to check it. If there is a basic calibration I need to do, I have missed it.

For now, I re-installed the block off plate and the fidle valve I fabricated, and am back to working things manually with a rocker switch from inside. I do not feel bad about this. It runs fine without the IAC. I just thought it would be nice to get that feature going. It is only a mild disappointment.

I contacted Inovate today, and they have received the controller I sent back to them. They say it will be repaired and returned to me within 2 weeks. So, at that point I can start really tuning the fuel table. I tackled this IAC task just to have something to do while I waited.

Now, if I run into this kind of trouble when I try to get the ignition switched over to the locked distributor and timing control output, I will be VERY disappointed. There are software choices I have to make at that point, and I hope I get it figured out. As I have said before, this is not my strength. Thanks again for your ideas and help. I do not take them for granted.



Sam

_________________