F225 ISC Valve - LED visualization study

[fairdeal]

this was fun.
Big Pine Key is sort of a backwater - but amazingly, we still have a Radio Shack
so yesterday I picked up 4 12V LEDS

The ISC has four coils, so there are four leads for the ECU to ground.

Backprobed the plug to parallel in the LEDs - and captured the result at key on.

several notable aspects:

- you can see the lights flashing well before you hear the sound. I don't think that's a speed of light/sound difference -
rather, than the valve movement is quiet UNTIL it is driven full stroke and is hammering against its travel limit

- as I recalled from earlier testing, after it has stopped moving the valve,
"for some reason" the ECU maintains power flowing to two coils.
This doesn't step the motor - the other coils would need power to do that -
but why are they "unnecessarily" continuously providing power?

This was noted in a recent thread, the poster questioned that is ISC "got warm" after sitting for a while with "key on".

BTW you can also hear the sound of the VST pump running; and the loud grating noise when the lights go out at key off is the Lenco tabs resetting.

Sorry its upside down - it was easier for me to touch the camera control that way.

Here's the video link:

https://vid.me/211Ca



the test setup:

[boscoe99]

With the motor idling in gear, what happens if you advance the throttle a bit? Do the lights change?

If the boat were in the water and moving first into the wind and then down wind, at idle RPM, would the ECU sense a change in load and make an IAC valve adjustment to try and maintain the RPM?

Those tabs do make a ruckus.

Thanks for the test. You are the go to test guy.

[99yam40]

Interesting that it keeps 2 coils energized .

Maybe it is to keep it from moving.
kind of like a brake

[fairdeal]

https://vid.me/Attl2

here's another video

begins with "key on" - but after the initial setting of the valve

then ~2 minutes of idling

very interesting pattern of lights,

as the ECU apparently "hunts" to manage the idle.



I was going to hook up YDS to watch the % opening values -

but Windows 10 is kicking my butt today - can't get the serial connector working

[boscoe99]

Fred, you have outdone yourself. Great work.

Very interesting. I see the ground being applied but damn if my tired ears can hear any change in the idle RPM. Might be con*****ing the RPM at some value that is not discernable.

Now we need someone with an F90 or F115, who thinks they have an idle problem, to do your test on their motor.

Might you have a clamp on ammeter to see the current flow when the light is illuminated? I can send you mine if needed.

I miss my Radio Shack as sorry as it had become before it went away.

[boscoe99]

I just thought of something.

What if the valve was disconnected? What would the ECU then do when it started sending information to the IAC valve but the valve was not responding? What would the engine RPM do?

[pstephens46]

Wonder why we never get any fish pictures from Mr. Fairdeal?
He fishes more than most of us combined....
.

[fairdeal]

well, I'm spoiled - I'm only interested in eating wahoo - not so plentiful.
If I catch tuna or mahi I release them; the freezer is full of that.

This is my best catch since I've been here, though -

what they call "square grouper"

[pstephens46]

Not healthy...lives too long or something like that.

Now you are getting picky....

I do like Wahoo. One of my favorites.

Call it the "white steak" on the grill...

[Jason2tpa]

well, I'm spoiled - I'm only interested in eating wahoo - not so plentiful.
If I catch tuna or mahi I release them; the freezer is full of that.

This is my best catch since I've been here, though -

what they call "square grouper"

Please tell me you're joking....Because if you're not, and you knew the right people, you're 30k richer. Not like I know what I'm talking about or anything.

[rodbolt17]

what is funny is somebody has no clue of how a speed/density EFI open loop system works.

watch the YDS screen when it is running.

notice how the idle is not stable.

that is how the system works.
it hunts.
it is part of the ECU's truth table.

it is looking for XYZ inputs so it can give ABC outputs.

the ISC has 12v anytime the key is on.

the ECU simply looks at all the sensors inputs and based on its internal mapping it outputs various signals to make the engine match its mapping.
it is really quite simple.

[99yam40]

what is funny is somebody has no clue of how a speed/density EFI open loop system works.

watch the YDS screen when it is running.

notice how the idle is not stable.

that is how the system works.
it hunts.
it is part of the ECU's truth table.

it is looking for XYZ inputs so it can give ABC outputs.

the ISC has 12v anytime the key is on.

the ECU simply looks at all the sensors inputs and based on its internal mapping it outputs various signals to make the engine match its mapping.
it is really quite simple.

Looks like they were trying to see how often the coils were were being called upon to ajust on a normally running motor.

Rodbolt do you know why 2 of the coils show to be energized when not calling for the valve to move?

seems he is monitoring not just having 12 volts to the coils(which it has when key is in the on position), but also when the grounds are being completed by the ECU(energizing the LEDs)

[panasonic]

Fairdeal that is very interesting thanks for taking the time to do that....

[rodbolt17]

it is why a good running 350 chevy carbed will always idle smoother than an MPI.

the EFI constantly hunts.
the ecu is mapped for X idle RPM yet constantly overshoots then undershoots.
it is simply how the system works and can be watched on the diagnostic programs.
all of them do it.
crusader,volvo and mercruiser stuff displays way way more information than the yds.

[99yam40]

But why are 2 of the coils energized when at key on after it settles down without motor even running?