My tuner can bring the idle up anywhere from 100 to 1000 rpms over stock, but it's all of the time not selective. This is where it would be nice to have a flip chip, so you can go to a high idle tune and then back to a performance or economy tune.

 

There are throttle cables that have a pull ****, and hook to the throttle body. My 03 F450 tow truck has one. Just pull it out until you reach the desired RPM and it holds until you push it back in. It costs about $30.

 

As stated, the IAC interrupt will set a code for idle speed error as well as a circuit fault. If you can live with the MIL being on all of the time, it will work fine. The PCM uses a PWM 12v signal switched on the low side to dither the IAC valve. During cruise the duty cycle goes to near 100%, so the valve should handle current.

The ECT mod will also set a code, probably a P0125 for insufficient coolant temp. The PCM expects to see a certain ECT after so many minutes after engine start and if it isn't maintained, a code is set and the MIL is turned on.

I would think the simplest solution would be the manual cable to the throttle body, but this would probably be the least factory looking.

How about a linear actuator connected to a pull cable under the hood? Use a DPDT momentary switch to control it.

Or, a rotary servo with a cam that could act on the throttle body linkage?

Or, a throttle kicker like we used to have on the carbs to control idle speed with the A/C on? They were just a 12v solenoid on an adjustable bracket that held the carb linkage partly open.

 

I too have found a higher idle would be nice at times.

This thread contains alot of info and links about this subject. Even a few folks with gassers talking about doing the mod and it working... don't know how it works through the different years of gassers though.

https://www.ford-trucks.com/forums/4...-switches.html

 

Actually, the IAC is a motor - turn it one way it opens, turn it the other way (reverse polarity), it closes.

It's not a variable voltage that controls it, but reverseable voltage - one way or the other.

I'd be more interested in a cable-operated affair, something with a piece of metal that would slide between the throttle level and the stop/set-screw that would keep the gas pedal slightly depressed. Getting the thickness right would be a problem, and under load, the idle would drop.

But with the lack of "check engine light" when the IAC is bad and not moving, causing all sorts of idle issues, I don't think the PCM would care.

 

Read more about why the PCM wouldn't care:

https://www.ford-trucks.com/forums/5...t-come-on.html

 

Art, it sounds like your response was directed toward my posting. I respectfully offer this:

I have cut several IAC solenoids apart and have never seen anything except a solenoid attached to a valve. There is no rotary motor contained within them, and there is no reversing of voltage. Of the two wires going to the IAC solenoid, one is powered from the EEC relay and provides 12v. This wire is usually red. The other is low-side switched by the PCM utilizing PWM, which on a DVOM will show as a varying voltage due to the RMS function. To truly see the functioning of the circuit you need an oscilloscope.

I have demonstrated this functioning to apprentices many times by grounding the PCM side of the circuit with the engine running. Give it a try and see what happens.

You can see the circuit design on page 24-4 of the 2002 Super Duty Wiring Manual as well as the functional description in the "Intake Air Systems" section of the 2002 PCED which states: The PCM determines the desired idle speed or bypass air and signals the IAC valve assembly through a specified duty cycle. The IAC valve responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine rpm and increases or decreases the IAC duty cycle in order to achieve the desired rpm.



Someone that is handy with electronics could come up with a PWM transistorized driver circuit controlled by a pot. Hooked into the PCM side of the IAC circuit with a relay, this could be used to control a high idle system. The only problem would be that this system, unlike what you get with the diesels, would not be able to compensate for varying loads such as the A/C compressor cycling.

 

What do you guys use a higher idle for anyway? Is it for electronic demands?

 

I'd like it for my winch or to recharge my battery if I don't plan on driving far and using a lot of amperage.

 

Subscribed for interest for my 5.4L 2v Expedition.