Megasquirt Support Forum (MSEXTRA)

Good point, but the V3.57 mainboard is slightly different. There isn't an IGBTOUT that I posted, Q16 needs to be removed and the middle pin where Q16 was connects to pin 36.

James

Ah, I understand now; I wasn't considering that it was an SMD board!

Thanks to both you guys - working as intended - at least in test mode. Now I need to dial it in .

Okay guys-before I go the tuner studio forum and cry for help-I'll ask this here.
As I stated earlier the stepper seems to be moving in and out smoothly. The problem is that it seems to be operating exactly opposite as what it should be. When I start the car the idle starts slow and ramps up as it runs. If I pull the stepper out and watch it as I turn the key on(ignition on) I can watch the pintle retract to what I think is an open position(correct?). Please look at me settings to see if I have stuff wrong.
I've got to say that this is VERY confusing and all the writes I've read haven't helped much. It doesn't help that the nomenclature has changed between write ups and firm ware. I'm having trouble just determining what is considered the home position?
I've tried changing homing direction , but have stuck with what is recommended. I at least have it good enough that the pintle is not shooting out of the body and across the floor anymore.
Enabling home position in test mode puts the pintle out to its closed position -correct?

When the step count goes down, the pintle should extend. If it doesn't, just reverse the IAC by simply swapping the wires on one of the stepper coils. That is, swap 1a and 1b; or similar to 2a & b. Don't swap the wires on both coils.

Thanks Bill, and happy holiday.
I thought I might need to change coil wiring, but the articles I read made it sound like you could remedy the situation in Tuner Studio. What further confused me is the position of the pintle with ignition on before starting-the pintle was all the way in, which to me looked open and in the correct position for cold start. So during cranking it must pop back out?

Well that didn’t work- so it must be in my set up in Tuner studio. I’m going to reverse the numbers and see what that does

So I pulled the stepper out and laid it on the fender. When I turn the ignition on it cycles from in ( open) to out and back in again and remains there . I would think this is correct since that would have the valve open for start. But after I cycled the stepper( ignition) off and on a couple of times I noticed the pintle slowly unscrewing itself from the motor which in turn left the pintle in the more closed position with every cycle of the ignition. So maybe need to limit something or locktight the threads in the pintle shaft?
The pic shows open position . If I cycle the ignition the shaft will slowly work it’s way out and I have to screw the pintle back in

Use the stepper test mode.
Lower step numbers = less air = pintle further out. If not, swap wires until it is.

Regarding homing, you can choose whether to home open or closed. Normal it to home closed (i.e. fully extended.) The behaviour you mention where the pintle gets a bit further out on each key cycle sounds normal - when installed the pintle will extend to the stop.

James

Also, change "power between steps" to "always on" or "holding". That gives much more positive holding of pintle position when the stepper is not moving. It probably isn't an issue for your testing now with the engine not running and no vibrations, but will be beneficial once the engine is running.

LocTite on the pintle threads??? No, NO; you want that thread to run freely! Putting LocTite there would be comparable to running LocTite in the crankcase instead of engine-oil...

Maybe this will help explain my confusion

https://youtu.be/sfXGdfsxjgQ

Do I understand correctly, you can turn that pintle with your fingers to screw it in/out? If so, I think your IAC valve is damaged BER (Beyond Economical Repair). The pintle should have a key-way or similar that prevents it from turning.

Well James said that seemed normal in earlier post?

Where did he say that? This thread, what day? I have certainly not seen every kind of stepper IAC valve, but I have never seen one that had a rotating pintle.

jsmcortina wrote:Use the stepper test mode.
Lower step numbers = less air = pintle further out. If not, swap wires until it is.

Regarding homing, you can choose whether to home open or closed. Normal it to home closed (i.e. fully extended.) The behaviour you mention where the pintle gets a bit further out on each key cycle sounds normal - when installed the pintle will extend to the stop.

James

I think we are talking he same thing

That says the pintle moves in-out, which is certainly true. However, I don't read anything there about the pintle ever rotating. Let's wait for James to comment again tomorrow

Copied from a DIY article

First, make sure that the idle control is set to “Stepper Valve”, not PWM or on/off idle control. For initial testing, we recommend using open loop instead of closed loop. Closed loop requires more complicated settings and has more that can potentially go wrong.
The time step size is how long the stepper driver will command an individual step. If the valve is perfectly dialed in, this will match the time it takes the coil move the motor through a single step. If this value is too low, the step is not completed, and the valve does not move. If the step is too high, the valve will move more slowly than it can – but otherwise there aren’t any consequences. Your best bet is to set this for 10 ms, then decrease until the valve no longer moves. Then add 0.5 to 1.0 ms.
4 wire valves that turn freely usually need to use “Always On” mode. Valves that are difficult to spin by hand usually need to use “Moving Only” mode; the same goes for all 5 or 6 wire valves.
The homing steps (called “start value” in older code versions) needs to be set to a large enough value that the valve retracts fully from any position the valve can reach during operation.
The current MS3 and MS2/Extra code allow you to specify if the valve closes or opens on startup. Regardless of which position it is set for, you need to set the number of homing steps high enough that it will move all the way to this position no matter where it starts

It is the threaded shaft that is able to rotate, not the pintle end itself. (I just double checked on a GM stepper idle valve I have here.)

James

Yes-the shaft that has the pintel end cap on it . rereading the article I need to change my mode to always on to start with.
Also this :
Problem: Idle speed is not consistent from one start to another at the same temperature.  Solutions: Usually, this is caused by the homing steps being set too low. Increase this value until the valve retracts fully; If the valve sometimes retracts fully, but not always, this may mean the steps are small enough that they do not always successfully move the motor. Try increasing the time step size.

4 wire valves that turn freely usually need to use “Always On” mode. Valves that are difficult to spin by hand usually need to use “Moving Only” mode

Well, I agree that implies you can turn the pintle, the only part you can get a hold on; but the article either doesn't apply to the typical GM-type I am familiar with, or it is just plain wrong. Yes, I have found errors with DIY info on steppers before... (how to reverse them).

I think James and I are in agreement that the pintle on our GM steppers cannot be turned more than a few degrees allowed by clearance in the key-way. In fact I can't even see the thread that turns unless the pintle pops out loose. The thread is all inside the snout of the motor housing.

OP, understand that I am not trying to prove that anybody is right or wrong. I am trying to alert you that your stepper may be damaged and will never work satisfactorily, no matter what settings you try. I also want to warn others to not force a pintle to move, either by lineal push/pull or rotation. When you install a stepper IAC you must be sure the pintle is retracted enough so that it doesn't "jamb" forcefully against the pintle seat in the TB as the IAC is fastened tight to the TB. Test Mode is, of course, ideal for retracting the pintle all the way to be safe.

Does anybody want me to post a photo of a couple of typical GM steppers, showing that anti-rotation key-way on the pintle; will that help clarify this?