MSefi.com read only forum (Jan.15,2018)

I've read this:

For example, the Ford PWM idle valves typically used with EDIS run best at a frequency of around 300-320 Hz. These are closed at zero duty cycle, and fully open at about 50%.

But still a little confused as to when the valve is open or closed. Am I closing the valve as the car warm's up or am I opening the Ford IAC valve when it warm's up

The valve should be open when cold and close as the engine warms up. At least that's what my GM IAC does.

http://www.megamanual.com/ms2/IAC.htm

So it should look like this then?

I am not familiar with your Ford IAC so I can't comment on the screen shot you posted, but it looks considerably different than the one I see in the default MS II w/B&G code.

I am merely saying that it is normal to allow more air in at cold temperatures (and more fuel of course) to maintain idle. Then, as the engine temperature rises the idle air is gradually decreased to achieve the required warm idle speed.

PWM of 0% means that the solenoid is fully energised all the time, and the valve is held shut, not allowing any air to bypass the throttle plate. The higher the PWM % number, the less time the solenoid is energised, and the valve is allowed to open and allow air to bypass the throttle plate to assist the warm-up procedure. The PWM happens at a high enough frequency to hold the valve in a certain position, not actually opening and shutting it, as it doesn't have enough time to shut between pulses that energise the solenoid. In the screen shot you provided, the PWM% of 50 at -20 Degrees and 0 at 160 degrees means the valve is fully open at -20 degrees, and will progressively (according to your settings) close up to 160 degrees, above which it will stay fully closed.

Stag76 wrote:PWM of 0% means that the solenoid is fully energised all the time, and the valve is held shut, not allowing any air to bypass the throttle plate. The higher the PWM % number, the less time the solenoid is energised, and the valve is allowed to open and allow air to bypass the throttle plate to assist the warm-up procedure.

So I guess my chart is correct then right? I want more air (fully open valve 50%PWM @ lower engine temp)and when warm/higher engine temp (closed @ 0% PWM)

From manual--->

For example, the Ford PWM idle valves typically used with EDIS run best at a frequency of around 300-320 Hz. These are closed at zero duty cycle, and fully open at about 50%.

Yes...your chart is correct. Just experiment with the points in the chart as the engine warms up in order to achieve a smooth transition from cold start (say 1300rpm) until hot idle (800rpm).

Thx

Panel, I am curios, how did you wire your IAC (being it only has 2 wires), I am currently working on my Volvo 940, with a Supercharged 5.0 in it, and am a little stuck, I might have mis-read something, or over looked another section....thanks for the heads up.

Try here first and then if no help I'll try to guide you through it. Some links are MSExtra but I think I wired mine the same way.

http://www.megamanual.com/ms2/IAC.htm#fidle

http://www.msextra.com/forums/viewtopic ... tang#60874

http://www.msextra.com/forums/viewtopic.php?t=27622

http://www.msextra.com/doc/ms1extra/MS_ ... .htm#Fidle

http://www.msextra.com/doc/ms2extra/MS2 ... .htm#Fidle

panel wrote:I've read this:

For example, the Ford PWM idle valves typically used with EDIS run best at a frequency of around 300-320 Hz. These are closed at zero duty cycle, and fully open at about 50%.

But still a little confused as to when the valve is open or closed. Am I closing the valve as the car warm's up or am I opening the Ford IAC valve when it warm's up

I still don't think my first question was really answered. Is the valve open or closed lets say if you where to have no power to this valve at all. Kind of like if it was disconnected. This should simulate a fully warmed up car....yes?

I just had the bus running and when it was fully warmed up the RPM seemed to get higher when using the graph I posted up higher in this thread.

Weather the valve is open or closed when warm or cold is besides the point(I understand this part) ......it's the part of if the valve needs to be opening during warm up. Which in turn could really be closing the air off.

Do you guys see my logic

Found this while searching the web:

The two wire idle control valves use the current through a single winding to open a plunger valve against the force of a spring. The amount of current is set by a pulse width modulator (PWM) amp. When power is removed the valve returns to its closed position.

The later three wire idle control valves use a rotary type valve and two windings. The rotary valve is opened or closed by the imbalance of current in the two windings and must be driven accordingly by the control circuit. For example, a 50% duty cycle PWM signal on both windings will produce no valve movement. When power is removed the rotary valve will remain in its present location. In general the three wire valves can handle larger volumes of bypass air

Well thought I'd report back on a couple of cold starts. Looks like my Ford IAC valve is fully closed at 100%. I also disconnected it when warm and no change in idle. This tells me then that I think I might be on to something

The manual says it's fully open at 50%.

Even when the motor CLT gauge is at 160 and the setting is at 50% it still idled real high. So I just kept upping that value till it ran at around 900RPM.(closing the valve etc.)I'll try it again tomorrow and see what happens.

Is anyone using the linear setting to make a nice line in the graph?

Found some more guys with the similar problems as me.

viewtopic.php?f=31&t=33459&hilit=ford+iac

viewtopic.php?f=30&t=38179&hilit=ford+iac

Panel,

I've given up on trying to reconcile the way my Ford IAC actually works with the way it "should" work. With two wires and PWM -polarity shouldn't be an issue, in other words, a current pulse should cause the pintle to retract

At 0% it's wide open, at 100% it's completely closed -just like when you remove the 2-wire plug.

After warm-up the IAC is at 100% which should be zero current flow -can't say for sure as I've not put the scope on it. I read at some point these (IACs) are not rated for constant use. I use the stop-screw on the throttle body to set low idle.

'66fb,

I was beginning to think I'd wired mine up backwards or something or I was the only one with this problem .

Thanks for the feedback.

100% should be maximum current flow.

Matt Cramer wrote:100% should be maximum current flow.

So if I have 100% in my last box lets say 160F and my idle is 1000RPM and I can disconnect the IAC valve which is what's happening right now then it looks as though I've wired the thing up wrong or something. Or is 100% maximum current flow correct for running temp on the car?

What I really don't want to do is have something burn out etc.

Matt...........here is my latest MSQ. Maybe there is something I've put in the wrong area or Are my 'Idle control' entries correct?

That file would have the valve closed with the engine at -40 and wide open when the engine is fully warmed up.

Matt Cramer wrote:That file would have the valve closed with the engine at -40 and wide open when the engine is fully warmed up.

Thanks Matt......I'll try this again in the morning then

Does this below pic look better ........Actually what I'll do for you is 'log' one for you/me to have a look at.

Marc,

It's not impossible that there are different Ford Idle valves out there, so I think you might have to test yours to see how it reacts.

If this was mine, I would do is try Idle PWM values of 25%, 50% and 75% in quick succession while the engine is relatively cool and running (That is, type them into the green highlighted row of the table and see what happens to the rpm). Then you should see very quickly which way opens the valve (higher rpm) and which way closes it (lower rpm). That should establish the 'direction' of the valve with respect to the processor output. It may be a little tricky if the engine wants to stall (or warms up very quickly), but you are mostly looking at the overall effect. If you can't keep the engine running, you might have to use the throttle stop to increase the engine rpm temporarily while doing these tests.

If the engine rpm doesn't change with changing PWM%, you need to check the software settings (make sure you have selected 'PWM Warm-Up' under 'Fuel Set-Up/Idle Control' [http://www.megamanual.com/mt28.htm#sd] and that you are not using the FIdle pin as a spare port [http://www.megamanual.com/mt28.htm#sp]), idle valve, the wiring, and MegaSquirt itself to find out why. A stim can be helpful for checking MegaSquirt, the idle LED should change brightness with changing PWM%.

I would also check if the 75% value made any difference over the 50% value. If it did, then I would try 80%, 85%, 90%, etc. to see at which value increasing the PWM% made no difference to the engine rpm. That would become your maximum Idle PWM% value. If 75% did not make any difference over 50%, then I would try 70%, 65%, etc. to see what the maximum value is.

Suppose from this you find that the engine rpm is increased at 75% over 50%, and engine rpm is higher at 50% than at 25%. Then you know that the valve open with increasing PWM%. Suppose you then do the next test an find that the rpm stops increasing at 90% (i.e. no faster than at 85%). Then your PWM Idle PWM curve should start at 85%, and end at 0% when fully warmed up (and note that you set your fully warmed up rpm with the physical throttle stop, not the idle PWM% software setting.)

Then tuning the PWM% is just a matter of doing a cold start, and adjusting the PWM% from the 85% value is a smoothly decreasing fashion to 0% percent at the temperature you consider fully warmed up. The best way to do this is to let the vehicle cool-down over night (you only get one cold-start a day), then start the vehicle, and while idling in the driveway adjust the PWM% values so the engine runs best (smoothest) in each bin as it warms up.

It may take a few tries to get it right (partly because the interpolation between bins can throw things off a bit at first - this is where it helps to have entered a smoothly decreasing set of values from the start).

Once that's done, you might have to re-tune your warm-up enrichments slightly to be optimal.

Lance.